Change signature of routemaster.

This commit:
* Changes the signature of routemaster to take an options hash instead
  of a directory string. This options hash requires `Router` and
  `directory` properties.
* Removes Express as a dependency. Users are now required to pass
  `express.Router` in via the `Router` option instead.
* Routing files are no longer required to return their routers.
* Tests and dev dependencies rejigged.
Change mocha reporter to spec
Add new rules to test/.jshintrc
Update README
Increment version number to 0.2.0
Merge pull request #1 from BrandwatchLtd/version-2

Routemaster version 0.2.0