Stub ActionSpec
Initialize Actions with scheduler to serialize on
Test and fix enabled/executing default behavior
WIP more enabled/disabled tests for Action
Merge branch 'swift-development' into action-tests
Improve ColdSignal and HotSignal debugDescription
Back `enabled` with an ObservableProperty

This avoids issues around duplicating side effects, like missing values
on `enabledIf`.
Test Action.execute
Remove “Differences from Rx” document

Resolves #1484.
Clarify that RAC is inspired by Rx, not based upon
Merge pull request #1623 from ReactiveCocoa/remove-differences-from-rx

Remove “Differences from Rx” document
Make file, function, and line properties internal

Consumers shouldn’t really need these, it’ll pollute any published
documentation, and we shouldn’t need to worry about backwards
compatibility for them.
Merge pull request #1626 from ReactiveCocoa/make-debugging-internal

Make file, function, and line properties internal
Merge pull request #1614 from ReactiveCocoa/action-tests

Action tests
Merge branch 'swift-development' into kill-subscription-terminology

Conflicts:
	ReactiveCocoa/Swift/Action.swift