OSX Tweaks

I made a few changes to make it possible to develop on osx, and to make the build system work. 

- the gitattributes file made it so that one of the snippers was ALWAYS modified, even after checkout, reset --hard, etc
- I removed the `os.path.realpath` in Typescript.py so the plugin would work when the folder is a symbolic link. 
- I added a better default path for osx (node is installed to /usr/local/bin by default). Is there a better way to do this?