Diff parser and pretty html generator

diff2html was revamped with:

- Added support for unified diffs

- New webpage

- Improved syntax highlight (thanks to @isagalaev from https://github.com/isagalaev/highlight.js)

- Improved diff highlighting colors

- Better file change identification

- Better identification of file renames, copys, changes, etc

- Added synchronised scroll to side-by-side mode

We use it at Codacy! Really cool project. Congrats