Add -[RACSignal deliverOnMainThread]
Queue events and drain them on the main thread.
Merge branch 'master' into deliver-to-ui
Make delivery code more similar to RACSubscriber.
Remove unnecessary nil check.
Revert to delivering one event per run loop.

This reverts commits 97da8702ebbfc6f869ca4a20b255a6825d31cc23, 07c927e976eaf7df76a2c73947d534ebcc8e7d12, ade0a6310bb86121a3142527f54cd74169ec0958.
Fix method brace style
Refactor -deliverOnMainThread to deduplicate code
Bring queueLength into each signal subscription
No need for a barrier upon incrementing

At least, I think this is correct, since we’re not trying to
synchronize with any other state at the same time.

/cc @jlawton
Add unit tests for -deliverOnMainThread
Merge pull request #1618 from ReactiveCocoa/pr/1425

-deliverOnMainThread redux
Update requirements to iOS 6 and OS X 10.8

It looks like the Xcode project specifies a minimum or OS X 10.8 SDK, and uses iOS 6.0 only features (strong properties with a type of `dispatch_queue_t`)
Minimum iOS version required for the Xcode project is 8.0
Merge pull request #1625 from tonyarnold/patch-1

Update requirements to iOS 8.0 and OS X 10.8