Put code coverage into appledoc header

![](http://blog.millermedeiros.com/wp-content/uploads/2013/12/I-have-no-idea-what-I-am-doing.jpg)

This fetches the stats from Coveralls and shoehorns them into the appledoc header. Will probably break horribly for non-GH repos and if there's no actual coverage data there, but it's a start :)
https://github.com/CocoaPods/cocoadocs.org/issues/187