set up backbone push state history
add content update action to api
change port number
clean up Content constructor

- only needs the parent directory relative to root-cms's root directory
- server now ensures path is set as id for the piece of content in the api json response
- to_json() wrapper method for internal data (front matter), category sorter now
  receives an array of Content objects and calls to_json, instead of
  receiving an array of Content already transformed to json
- general cleanup
Merge pull request #8 from carrot/update-content

Update content API & Cleanup