What is claimed is:1. A heated firearm stock, comprising:(a) a firearm stock having a pistol grip portion;(b) an electrical power source having a first contact and a second contact and an electrical potential between the first and second contacts;(c) a heated insert positioned on the pistol grip portion of the firearm stock, the heated insert including a thermally-conductive electrically-insulating portion and an electrical resistance heating element disposed in direct contact therewith and adapted to conduct an electrical current and to warm the thermally-conductive electrically-insulating portion in response to the electrical current, the electrical resistance heating element having first and second electrical terminals for establishing an electrical connection therewith;(d) a first wire connecting the first terminal of the heated insert to the first contact of the electrical power source; and(e) a second wire connecting the second contact of the electrical power source with the second terminal of the heated insert thereby completing an electrical circuit which includes the electrical power source and the heated insert such that when electrical current flows through the electrical circuit the heated insert is heated to provide a heated surface on the pistol grip portion of the firearm stock.2. A heated firearm stock, comprising:(a) a firearm stock;(b) an electrical power source having a first contact and a second contact and an electrical potential between the first and second contacts;(c) a heated insert positioned on the firearm stock, the heated insert including(i) an electrically and thermally insulating first insert portion,(ii) a thermally conductive and electrically insulating second insert portion, and(iii) an electrical resistance heating element disposed between the first and second insert portions and adapted to conduct an electrical current and to warm the second insert portion in response to the electrical current, the electrical resistance heating element having first and second electrical terminals for establishing an electrical connection therewith;(d) a first wire connecting the first terminal of the heated insert to the first contact of the electrical power source; and(e) a second wire connecting the second contact of the electrical power source with the second terminal of the heated insert thereby completing an electrical circuit which includes the electrical power source and the heated insert such that when electrical current flows through the electrical circuit the heated insert is heated to provide a heated surface on a portion of the firearm stock.3. The firearm stock of claim 2, wherein the electrical power source is a battery pack.4. The firearm stock of claim 2, wherein the electrical resistance heating element includes a single strand of Nicrome wire disposed in a reticulated fashion between the first and second insert portions.5. The firearm stock of claim 4, wherein the firearm stock has a recessed portion adapted for receiving the heated insert.6. The firearm stock of claim 5, wherein the heated insert is adapted to conform to the recessed portion of the firearm stock.7. The firearm stock of claim 2, wherein the firearm stock has a pistol grip portion and the heated insert is wrapped at least partially around the pistol grip portion of the firearm stock.8. A heated firearm stock, comprising:(a) a firearm stock;(b) a battery compartment in the firearm stock having first and second contacts for maintaining an electrical connection;(c) at least one battery disposed in the battery compartment and electrically connected with the first and second contacts of the battery compartment;(d) an electrical switch adapted to be placed in opened and closed positions;(e) a heated insert positioned on the firearm stock, the heated insert including(i) an electrically and thermally insulating first insert portion,(ii) a thermally conductive and electrically insulating second insert portion, and(iii) an electrical resistance heating element disposed between the first and second insert portions and adapted to conduct an electrical current and to warm the second insert portion in response to the electrical current, the electrical resistance heating element having first and second electrical terminals for establishing an electrical connection therewith;(f) a first wire connecting the first terminal of the heated insert to the first contact of the battery compartment;(g) a second wire connecting the second contact of the battery compartment with the switch; and(h) a third wire connecting the electrical switch to the second terminal of the heated insert thereby completing a switchable electrical circuit which includes the at least one battery and the heated insert such that when the electrical switch is placed in the closed position electrical current flows through the electrical circuit and the heated insert is heated to provide a heated surface on a portion of the firearm stock.9. The firearm stock of claim 8, wherein the electrical resistance heating element includes a single strand of Nicrome wire disposed in a reticulated fashion between the first and second insert portions.10. The firearm stock of claim 8, wherein the firearm stock has a recessed portion adapted for receiving the heated insert.11. The firearm stock of claim 10, wherein the heated insert is adapted to conform to the recessed portion of the firearm stock.12. The firearm stock of claim 8, wherein the firearm stock has a pistol grip portion and the heated insert is wrapped at least partially around the pistol grip portion of the firearm stock.13. The firearm stock of claim 8, wherein the firearm stock has a butt end and the battery compartment is situated inside the firearm stock near the butt end of the firearm stock.14. The firearm stock of claim 13, wherein the firearm stock has a pistol grip portion and the heated insert is wrapped at least partially around the pistol grip portion of the firearm stock.15. The firearm stock of claim 14, wherein the electrical switch is mounted at a bottom of the pistol grip portion of the firearm stock.