Gitx dev diff word highlight

Integrated an inline word diff algorithm to highlight changed words in diffs. similar to github's hybrid mode. 
Addressing  #168

The javascript implementation is based on John Resig's javascript diff algorithm described here: http://ejohn.org/projects/javascript-diff-algorithm/

![gitx diff](https://f.cloud.github.com/assets/26716/950507/62d23702-0390-11e3-8bde-7691eaa77473.png)