Add parslet ~> 1.0 as a dependency.
First stab at a SPF record parser.

* Derived from http://www.ietf.org/rfc/rfc4408.txt, Appendix A.
Only load codeclimate if CODECLIMATE_REPO_TOKEN is set.
Added more captures.
Adjusted the parser so :digit is nil, if no digits are given.
Began adding specs for the Parser.
Optimized domain_spec by matching macro_string.

* Instead of trying to match domain_end and toplabel, just let
  macro_string match the remaining string.
* Change macro_string to repeat(1) and add macro_string? for
  unknown_modifier.
Adjusted captures and added more specs.
Fixed a few rules.
All speced.
Adjusted the mx and a specs, since domain_spec gobbles the /cidr-length.
Better expose the cidr-length of IPs.

* Apparently Ruby's IPAddr doesn't expose the cidr-length.
Added Transforms and adjusted the parse tree.
Added Record.
Require spf_parse/record.
Updated the util to use Record.
Convert macro letters and qualifiers to Symbols.
Allow Modifier value to be nil.
Allow the Directive value to be nil.
Added Record#each.