Add support for updating CocoaPods the gem, without updating the App

[orta]

Looks like we can end up behind on App releases, given the complications of the setup and the general activity of the original people behind it.

Ideally people should be able to update the CP release themselves.

Sidenote: this may not be entirely feasible. In #370 we had to add new static libs to the compiled ruby in order to support new calls used by CP + gems. This may need to happen again in the future.

[orta]

#157 however may make this easier, would recommend trying to continue with that.