Update ruby-rspec-mocks to 2.11.2

### 2.11.2 / 2012-08-11
[full changelog](http://github.com/rspec/rspec-mocks/compare/v2.11.1...v2.11.2)

Bug fixes

* Don't modify `dup` on classes that don't support `dup` (David Chelimsky)
* Fix `any_instance` so that it works properly with methods defined on
  a superclass. (Daniel Eguzkiza)
* Fix `stub_const` so that it works properly for nested constants that
  share a name with a top-level constant (e.g. "MyGem::Hash"). (Myron
  Marston)

### 2.11.1 / 2012-07-09
[full changelog](http://github.com/rspec/rspec-mocks/compare/v2.11.0...v2.11.1)

Bug fixes

* Fix `should_receive` so that when it is called on an `as_null_object`
  double with no implementation, and there is a previous explicit stub
  for the same method, the explicit stub remains (rather than being
  overriden with the null object implementation--`return self`). (Myron Marston)

(taca)