Add cloned CocoaPods specs repo to OS X image




currently there is no pre-cloned version of the CocoaPods Specs repository on the OS X machines. Since CocoaPods switched to using a full clone for performance reasons instead of a shallow clone each build clones the full repository.
If there would be a pre-cloned version of the specs repository it would just pull on top of it resulting in a few seconds instead of about 2 minutes.

I would love to see this change soonish as it is the step thats takes the most time in my build currently.

More information:

Bundle ~/.cocoapods with Xcode images
closed #2