Highlight the example that failed when an exception is raised
Add functional test for unhandled exceptions thrown in examples

Exposes `-[QuickSpec example:failedWithException:]` as a public method,
and uses it to intercept an exception raised during an example in order
to make assertions on it.
Add unit tests for Example._callsite
Add Objective-C functional test for unknown exceptions
Example.swift: Remove _file and _line properties in favour of objc-bridged Callsite class
Merge branch 'master' of http://github.com/modocache/Quick into example-exceptions

Conflicts:
	Quick/Core/QCKDSL.h
Merge pull request #41 from sharplet/example-exceptions

Catch exceptions thrown during examples and highlight the failed example in Xcode