The constant tested is defined in an initializer, and these are not
loaded when using fast_spec_helper. When running just this test file, or
when running this test first this can lead to test failures. To fix this
we just use spec_helper instead of fast_spec_helper.

- Add mail interceptor the signs outgoing email with SMIME
- Add lib and helpers to work with SMIME data
- New configuration params for setting up SMIME key and cert files