Log Message:
Update ruby-rspec-mocks to 2.13.1.

### 2.13.1 / 2013-04-06
[full changelog](http://github.com/rspec/rspec-mocks/compare/v2.13.0...v2.13.1)

Bug fixes

* Allow a block implementation to be used in combination with
  `and_yield`, `and_raise`, `and_return` or `and_throw` (Myron Marston).