since the passed in errorType could be a custom user function,
we instead detect if its an instanceof Error by using a Surrogate
(inspired by Backbone's use of surrogacy)
- It still supports no expected, which means that something was thrown
- Expected value is now tested via equality in order to pass
Adding toThrowError:
- toThrowError() passes if an Error type was thrown
- toThrowError(String) & toThrowError(RegExp) compare Expected to the Error message
- toThrowError(Error constructor) compares Expected to the constructor of what was thrown
- toThrowError(Error constructor, String) & toThrowError(Error constructor, RegExp) compares both the Error and the message
Also, equality now handles Errors, enforcing the message as part of the equality.
