Added draft of interface of methods for two-way binding.
Added some basic tests.
Document +[RACSignal createSignal:] side effect behavior
Document general <RACSignal> side effect behavior
Document RACSequence side effect behavior
Document that -sendError: should accept nil
Make sure sending a nil error doesn't blow up any <RACSubscriber>
Changed the names of the methods.
Removed shorthand method.
Added shorthand method to iOS-specific category.
Merge pull request #164 from github/side-effects-documentation

Attempt to document how signals and sequences invoke side effects
First draft of implementation.
TomDoc style for <RACSubscriber> parameters
Remove unnecessary import
Merge pull request #165 from github/nil-errors

Document that -sendError: can be given nil
Changed rac_bind:signalBlock:toObject:withKeyPath:signalBlock: to accept nil signal transformation blocks.
Revert "Added shorthand method to iOS-specific category."

This reverts commit 730f87ccb28432cb5b7b8f081de095c25ee46056.
Added test for race conditions when bound objects are changed simultaneously.
Removed test for transformation application. It's best left as an implementation detail.
Send replayed values on the subscriptionScheduler in RACReplaySubject

Also cancel replaying if the subscription to the subject is disposed.