Fix should in helper

**This is a follow on from #134.**

Due to the new `expect` syntax in RSpec, see [this blog post](http://myronmars.to/n/dev-blog/2012/06/rspecs-new-expectation-syntax), the `email_spec` helpers have been breaking when they use `should` in some cases.

This is when developers have, as some recommend, disabled `should` in their specs. As such I have bypassed `should` in the `email_spec` helpers.