history viewer implementation
new jscs rule
New style for history tab.

- Now everything it's in a single place (the tab), no popups anymore.
- On the left you can see the history of commits with users avatars took from Gravatar or generated by CSS (user choice).
- Clicking on a commit, the choosen one is loaded on the right side of the history tab.
- Comments are now formatted using markdown.
some fixes to rebase
rebase implementation
rewrite merge check to be more effective
better event logging
merged getHistory function
fix diff dialog
rewrites
rewrite more
jscs
changelog...
Merge pull request #358 from zaggino/rebase-plus-fez-history

Rebase feature + part of history by @FezVrasta