`make` does not create the binary in `bin/`, causes subsequent commands to fail

[jmarhee]

When make (defaults to compile) runs, it creates the binary in the project root, not bin/ so operations like make install and make clean (which does include both paths)` don't complete:

docker-machine-driver-metal/Makefile

Line 60 in 323f06e

cp bin/$(current_dir)/$(current_dir) /usr/local/bin/$(current_dir)

Would it be preferable to update the instructions to no longer reference bin/, or have it handle a bin directory to copy to/clean up from? Quick fix either way.