Add ruby-version and ruby-gemset
Allow #from return type to be configured

* Add default from configuration of :email
* Extract shared examples for email address config and apply them to
  both #to and #from
* Document `from` options
If the email body is nil, don't try to split it again

 - Break blocks into private methods
 - Better method naming and merged regexes together
 - Switch back to slash delimited regexes

Closes #71