Oh, I just noticed that this change doesn't include the update from #171 to the `--install-option` flag.

I strongly recommend removing `--target` and making the `--install-option` => `--install-option="--prefix=$NUPIC_INSTALL"`

Also, due to the numerous problems that can happen during the build, I strongly recommend adding back the three verbose flags `-v -v -v` to the pip install commands.

CC: @oxtopus @scottpurdy @breznak