Simplify demos' Podfile's

* `source` is optional again in CocoaPods 0.35.x.
* Set required Pods directly instead of defining `import_pods` to simplify.
Adjust Demos' deployment targets
Fix Demos' warnings
Fix for registeredClasses during program launch
Restoring to project's style of preferring NSUInteger
Merge pull request #416 from rivera-ernesto/update_demos

Update demos
Merge pull request #413 from mackworth/master

Fix for registeredClasses crash during program launch