Create task sections for collection class documentation.
Cleanup cross-referencing in documentation.
Add respondsToSelector enumeration [wip]
Improve documentation
Minor changes to structure, formatting and wording.
Merge branch 'documentation' into responds-to-selector

Conflicts:
	Classes/NSArray+SafeCast.h
	Classes/NSDictionary+SafeCast.h
Deprecate misspelled methods in favor of correct spelling.
Add separate implementation and tests for deprecated methods. Wouldn't want to break anyone ;)