Add CocoaPods spec and License

So, expanding on my initial pull request: 

I use [CocoaPods](https://github.com/CocoaPods/CocoaPods) to manage dependencies in my projects (like RubyGems + Bundler in Ruby). 

For one of my most recent projects, [Induction](https://github.com/Induction/Induction), I was interested in using your `LineNumbersView` class. In addition to the compiler fixes from my other pull request, adding a Pod Spec would allow NoodleKit to be distributed through CocoaPods.