- updated to version 3.2.1
Bug Fixes:

* Add missing `rspec/support/differ` require so that rspec-mocks can be
used w/o rspec-expectations (which also loads the differ and hided the
fact we forgot to require it). (Myron Marston, #893)
* Revert tracking of received arg mutation (added in 3.2.0 to provide an
error in a situation we can't support) as our implementation has side
effects on non-standard objects and there's no solution we could come
up with that always works. (Myron Marston, #900)