Fix for assert_select_email which is currently non-functional

A pull request to fix assert_select_email which is currently
non-functional in Rails 3-0 and 3-1...

https://github.com/rails/rails/pull/2499

+1's

Thanks,
Andrew

P.S.
Other pull requests still waiting for approval in Rails 3-0 and 3-1...
https://github.com/rails/rails/pull/2485
https://github.com/rails/rails/pull/2497