Support messages with new line characters

[dnlsng]

Without this change, the bot would ignore any messages with new line characters.

This is useful in the case where you would want to do something like this:

@respond_to('(.*)', re.DOTALL)

to match all text including new lines.

I can't think of a case where this would be undesirable.

[jtatum]

Please add/update functional/unit tests for this behavior.

[lins05]

ping @dnlsng