adding database option.
adding database option.

Allows user to choose which database the migrations
are run on.
paltman-archive/nashvegas,jpic/nashvegas,paltman/nashvegas,coffindragger/nashvegas,jpic/nashvegas,dcramer/nashvegas,coffindragger/nashvegas,GunioRobot/nashvegas,binarydud/nashvegas,GunioRobot/nashvegas,peterbe/nashvegas,dstufft/nashvegas,dstufft/nashvegas,iivvoo/nashvegas,jonathanchu/nashvegas,peterbe/nashvegas,marcinn/nashvegas