Document Rx equivalents
First pass at a "Differences from Rx" document
Document high-level interface equivalence
Embolden the class names for better readability
Put notable method differences into a list
Put acronyms in parentheses
Merge branch 'master' into rx-differences
Use qualified names for IObserver methods
Remove parentheses from C# method names
Specify the overload of Merge that -flatten: corresponds to
Remove parentheses in standalone document too
Merge pull request #265 from github/rx-differences

Document major differences from Rx
Use a mutable set for -rac_addDeallocDisposable:

It's synchronized anyways, and the speedup is ridiculous.
Only need to replace the associated object if the set is new
Merge branch 'mutable-dealloc-disposables' into disposable-optimization