Osx fixes

This is a dirty hack (I don't really expect you to accept this PR, more just wanted to show what I was talking about in my issue), that changes the plugin to search `sublime.Window.folders()` for `.hhconfig` as well as the folder of the current file. 

It also includes a small function that will search for `hh_client` on your $PATH, instead of hoping it'll just be there. Both have been tested and appear to work in OS X :)