We should have a singleton store that handles all communication with GitHub, caching, and so forth, rather than passing managedObjectContexts and GitHub instances around.
Until then, pass that GitHub instance around, so we can fetch the comments from an issue.
Issues are referenced by number, so expose the number property of GHIssue.
* Move the Core Data stack out of the app delegate into a singleton.
* The GHStore vends the shared GitHub instance
* The GHStore also vends its persistent store coordinator.

Individual view controllers can use the shared to coordinator to create their own managed object contexts and fetch requests.

This is based on a conversation with Core Data team manager Ben Trumbull wherein he expressed that managed object contexts are small and should be used for loose coupling rather than sharing a context, which breaks down across threads, while per-thread contexts on a single coordinator works fine.
* Add a model object for GitHub comments.
* Add an entity for GitHub comments.
* Relate issues to their comments in the managed object model.
* Managed object classes now expose named constant for their entity name.
* Added a model object for GitHub milestones.
* Implement loading of issue comments.
* Tapping an issue now loads its comments.
* Replace the boilerplate segue code with something that works.
* Remove some log statements.
* Factor out some inline contents.
Add the original body text to the talk view via the section header.
Merge branch 'master' of https://github.com/lemurs/Lemacs

Conflicts:
	Lemacs/LEAppDelegate.m
Update Cocoapods

Add HockeySDK