Enhancement to auto complete current path

Enhancement to auto complete current path, https://github.com/FredrikNoren/ungit/issues/37.

Uses jquery-ui and get rest API to get all directories in current path and allow users to select on the go.


![screen shot 2013-08-27 at 2 41 59 pm](https://f.cloud.github.com/assets/5281068/1039096/e7f8276a-0f76-11e3-91ca-2f0f3e56c5af.png)