* Swap out gopass dependency
Remove github.com/mewbak/gopass in favor of github.com/howeyc/gopass
* Add Windows to Makefile and build_release
Added Windows/386 and Windows/amd64 to the Makefile. Some minor changes
needed to be made to build_release to give the windows binary the ".exe"
extension.
* Makefile: remove windows/amd64