Added parslet ~> 1.0 as a dependency.
First stab at a DKIM parser.

* http://www.ietf.org/rfc/rfc4871.txt
* https://www.ietf.org/rfc/rfc2045.txt
Added basic captures.
Added a missing rule for dot_atom_text.

* https://www.ietf.org/rfc/rfc2822.txt Section 3.2.4.
Started adding transform rules.
Added a Key class.
Added Parser.parse.
Only load codeclimate if we have the token.
Support sequence tag values and symbolize '*'
Began adding specs for Parser.
Alias the fields to human readable names.
Added specs for n= and p=