Log Message:
Update ruby-rspec-expectations to 2.12.1.

### 2.12.1 / 2012-12-15
[full \ 
changelog](http://github.com/rspec/rspec-expectations/compare/v2.12.0...v2.12.1)

Bug fixes

* Improve the failure message for an expression like
  `{}.should =~ {}`. (Myron Marston and Andy Lindeman)
* Provide a `match_regex` alias so that custom matchers
  built using the matcher DSL can use it (since `match`
  is a different method in that context).
  (Steven Harman)