module.pip: added doc for new option "use_wheel"
module.pip: added doc for new option "use_wheel"

pip state and module got new option for pip>=1.4 called "use_wheel". State got properly updated doc for this change, but module not. This commit adds two lines of doc for pip module too.
saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt