Unescape special Slack Characters

[Startouf]

Slack performs encoding of special characters & < >. Those should be unencoded by the app but currently aren't.

So when in slack I type @myBot find students of MSc & MBA what is actually returned by match is

#<MatchData "find students of MSc &amp; MBA"

[dblock]

As long as we preserve backwards compatibility or make a clear breaking change and allow raw data to be retrieved I'd take a PR.