Feature: Implement yesno.mockMatchingFunction()

[keithcom]

Add a mockMatchingFunction method to the yesno class. This method will be passed a callback function that will be used to override the default internal matching function for matching requests with rules or the recorded mock array. The callback will be called with an object:

 {
  currentRequest,   // object with the request being processed
  recordedMocks,   // array of recorded mocks
  mockRules,          // array of rules
  maxMockCount   // the maximum number of times a mock can be used (defaults to 1, 0 is unlimited)
}