Log Message:
Update ruby-flexmock to 2.3.5.

2.3.2

* Make test-unit make_assertion compatible with new code.

2.3.3

* Define should_expect on partial mocks as well.
* Fix unused variable

2.3.4

* Workaround Ruby 2.0.x brokenness w.r.t. singletons of classes

2.3.5

* Avoid deprecated Fixnum warnings on Ruby 2.4.0.
* Add a LICENSE.txt file.