libextobjc 0.3.1-beta20140207 - remove experimental / broken features (just like post 0.3 upstream already did)

* Tagged version of upstream repo
* Upstream dev removed experimental and broken features from post 0.3 that do not work in various configurations (e.g. arm64).
* Basically, the previous podspec is a non-starter on any modern iOS7 dev that tries to compile with 64 bit support, and mainly because of the dependency on libffi ... which was only needed for an experimental feature, which upstream removed from master, and moved all experiments to another branch. This new spec simply acts as a holdover until upstream decides to tag another version.