Updated datasource to use CocopPods' public API

The big idea behind this request is I switched the datasource from the local, Ruby webserver to Cocopods public API. That way, folks can clone this repository and immediately build the project in XCode without any further configuration.

The other changes I made removed as much unnecessary code as possible and updated the code to modern Objective-C. I did this for those (myself included) who are using this repository to learn; the less code they see, the easier it will be to understand.

Other changes
- Put XCode in hard-mode and fixed all warnings.
- Removed the unused files OBJMasterViewController and OBJDetailViewController
- Removed unnecessary #imports
- Removed the attribute "strong" from properties, since all properties are strong by default
- Replaced return type "id" with "instancetype" on initializers
- Added a refresh control to the master list of pods
- Made indentation changes based on the NYT Objective-c style guide
- Added a .gitignore and a README.md