Introduce Slack chat room.
Fix visibility of RACScheduler+Subclass.h

It should be public for consumers to use, just like RACQueueScheduler+Subclass.h.
Merge pull request #1387 from ReactiveCocoa/fix-scheduler-subclass-visibility

Fix visibility of RACScheduler+Subclass.h
Rephrase note
Merge pull request #1381

Fixes #871.
Point more directly to the "What to do" part for Slack

If you arrive at the top of that issue it's super confusing, link more towards the anchor where people are dropping in Emails
Merge pull request #1388 from paulcbetts/patch-1

Point more directly to the "What to do" part for Slack
Move to specta/specta, specta/expecta, and XCTest
Only build the active architecture to test iOS
Merge pull request #1393 from ReactiveCocoa/xctest

Move to specta/specta, specta/expecta, and XCTest
Lift with a signal of tuples of arguments.
Merge pull request #1398 from ReactiveCocoa/lift-with-signal-of-arguments

Lift with a signal of tuples of arguments.
Referencing the right class in the RACScheduler method deprecation message.
Merge pull request #1401 from JaviSoto/patch-1

Referencing the right class in the RACScheduler method deprecation message