[Buildbot] #3184: Rewrite MailNotifier to use Data API

[Buildbot trac]

#3184: Rewrite MailNotifier to use Data API
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Reporter:  dustin  |      Owner:
    Type:  task    |     Status:  new
Priority:  major   |  Milestone:  0.9.0b1
 Version:  master  |   Keywords:
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 Note that the tests for !MailNotifier mock a lot of things out -
 incorrectly, now, so don't trust the tests!

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Ticket URL: <http://trac.buildbot.net/ticket/3184>
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