feat: changelog / release tasks

Fixes #62
You can now use `gulp changelog` to generate the changelog, and `gulp release` to build dist / build docs / generate the changelog / update the package.json and bower.json files.

Read the README.md update to know more about commits validation.
You should add the commit hook to validate your commits:
* `cd <famous-angular-repo>`
* `ln -s ../../validate-commit-msg.js .git/hooks/commit-msg`

The following types are accepted in the commit messages:
- feat
- fix
- docs
- style
- refactor
- perf
- test
- chore
- revert

But only feat/fix/docs/perf will be in the changelog.

Here is an example of the changelog generated:

<a name="0.0.13"></a>
# 0.0.13 (2014-05-25)


## Features

- Added the changelog and release gulp tasks
 ([a0406e1a](https://github.com/Famous/famous-angular/commit/a0406e1a62cbbefe3bedc8a8b01af7e27385f824),
 [#62](https://github.com/Famous/famous-angular/issues/62))
- Added validation commit msg file
 ([a3b57051](https://github.com/Famous/famous-angular/commit/a3b570516e0938f961c887600dd59e582a12c2de))


## Documentation

- updated the list of accepted types in the commit messages
 ([334bc7a6](https://github.com/Famous/famous-angular/commit/334bc7a671985edee07f39a5d1e68e6cbe113a30))
- updated the contribute section to include the commits validation
 ([442cb0c9](https://github.com/Famous/famous-angular/commit/442cb0c9ca4c7ebdd05b80b950cb677b1f8428bc))