Don't add 'bin' to $PATH

This is a terrible idea - I could put bin/ls somewhere, and trick you in to running Bad Things. If you're running stuff locally, do it explicitly like ./bin/x, or `bundle exec` for ruby

Alternatively if you want this on your path, set something up in your own .profile or manifest - shouldn't be forced globally in an un-modifiable manner.

Re-submitting because boxen/puppet-boxen#42 got closed.