Nimble 0.2.0

Changes in this release:

• Change: Objective-C matchers will now all properly reject nil values. Use beNil() to match against nils.
• Change: beEmpty() matcher no longer matches against nil
• Change: equal() uses Swift's built-in equality comparison.
• Change: Make objective-c matchers explicit about not accepting any arguments.
• Removed: Undocumented beOneOf() matcher that was Swift-only.
• New: expect().withTimeout() in objective-c for custom timeouts of async matchers.
• New: Added Podspec for Cocoapods' Swift Branch
• New: Documentation comments for Swift matchers
• New: NonNilMatcherFunc which supports emitting a consistent nil error message. Matchers that use this still need to safely process nils.