Log Message:
Update ruby-rspec-core to 2.13.0.

### 2.13.0 / 2013-02-23
[full changelog](http://github.com/rspec/rspec-core/compare/v2.12.2...v2.13.0)

Enhancements

* Allow `--profile` option to take a count argument that
  determines the number of slow examples to dump
  (Greggory Rothmeier).
* Add `subject!` that is the analog to `let!`. It defines an
  explicit subject and sets a `before` hook that will invoke
  the subject (Zubin Henner).
* Fix `let` and `subject` declaration so that `super`
  and `return` can be used in them, just like in a normal
  method. (Myron Marston)
* Allow output colors to be configured individually.
  (Charlie Maffitt)

Bug fixes

* Don't blow up when dumping error output for instances
  of anonymous error classes (Myron Marston).
* Fix default backtrace filters so lines from projects
  containing "gems" in the name are not filtered, but
  lines from installed gems still are (Myron Marston).
* Fix autotest command so that is uses double quotes
  rather than single quotes for windows compatibility
  (Jonas Tingeborn).
* Fix `its` so that uses of `subject` in a `before` or `let`
  declaration in the parent group continue to reference the
  parent group's subject. (Olek Janiszewski)