Merge pull request #471 from levibostian/objective-c-memory-management

Objective-C memory management.
Add @autoreleasepool as alternative to NSAutoreleasePool object.
Move statements out of @interface that did not allow file to compile. Fix various typos/confusing wording.
Remove broken Apple website link to Learning Objective-C and replaced with Programming with Objective-C Apple book link.
Edit code for all snippets to compile properly. Re-word some descriptions.
Merge branch 'objective-c-refactor' into objective-c-methods
Add more examples of methods available to objects.