Publish GenumKit.framework on CocoaPods trunk

[AliSoftware]

They will probably be useful only to other people wanting to create another CLI (not really suitable for integration in an iOS project for example), so not sure it's worth pushing to trunk?
but doesn't prevent from having a Podspec in the repo for people wanting to point to it anyway.

[AliSoftware]

The GenumKit framework is now exposed as a pod (via #30)

I haven't pushed it to pod trunk yet because I want to do #24 and have a better API before officially releasing the framework, so I'll keep this PR open to remind me to push it to trunk once everything is cleaner and the API is more settled.

[AliSoftware]

Closing this because we're gonna split GenumKit in two separate frameworks, one containing the specific Stencil Nodes & Filters to Swift (StencilSwiftKit?), and the other for the parsing of input specific to SwiftGen (SwiftGenFramework?). We might even want to put both of those in separate repos.