Bumped pod spec version to 1.1.1

Several bugs have been fixed since the `1.1.0` release on CocoaPods. In particular, `1.1.0` has two compiler warnings due to checking for `respondsToSelector` on non-existent method signatures.

Please tag the latest `master` commit as `1.1.1`, merge this change into the main repo, and <a href="http://guides.cocoapods.org/making/getting-setup-with-trunk.html">push to trunk</a>.