Fixed README.

docpad.coffee was renamed to docpad.js on the issue #67, but the README wasn't changed :P
Updated README to use github read-only url.

* Using github read-only url, so users without a github account will be able to clone this repo, goodbye 'Permission denied (publickey)' error :P
Merge pull request #69 from lucasdavila/master

Some enhancements to README