Let users override only options they care about.
Let the user specify the {{{ edit }}} replacement.
Let the user specify custom layouts
Removed deprecated modules and added some new features

- Removed dependency on the deprecated github-flavored-markdown. Using
  "marked" instead.
- Moved up to the latest "mustache"
- Added an "exclude" config option
- Fixed URL generation
Merge pull request #11 from gburca/master

Let users override only options they care about.