Log Message:
Update ruby-flexmock to 2.3.0.

2.3.0:
 - implemented validation of call arity for partial mocks. By setting
     FlexMock.partials_verify_signatures = true
   flexmock will verify on partials that the number of arguments, and the
   keyword arguments passed to the mocked call match the existing method's
   signature

2.2.0:

 - #new_instances now mocks the #initialize method instead of mocking after the
   allocation was done. This allows to do mock methods called by #initialize
   itself. Behaviour when the allocator is explicitely provided is left
   unchanged, which means that the old behaviour is still available by passing
   :new to new_instances.