Force controller spec to use sendgrid adapter

spec/features/adapters_and_email_spec.rb:9 was intermittently leaking the
configuration across tests and causing the controller spec to think it was
using the mandrill or cloudmailin adapter. Instead it should default to
sendgrid, which matches up more closely to the sample email params we're
posting to the action.

Further changes:

* Formatting and spacing, newlines after blocks, etc.
* Limit to 80 chars
* Move a method up in mandrill adapter spec for easier reading/comprehension