Add my regression tests

Ran tests on ocw2 with:

cd /srv/dropbox/Dropbox/OpenCMLRepo/Test/openobject-addons-7.0
/home/jbq/oe run-tests --db_host=192.168.1.10 -d cmlid-test --addons ../../../openerp-web-7.0/addons,. -m mail.test_mail_gateway
Fix detection of MIME type in message_parse()

Be careful, content-type may contain tricky content like in the
following example:

Content-Type: multipart/related;
  boundary="_004_3f1e4da175f349248b8d43cdeb9866f1AMSPR06MB343eurprd06pro_";
  type="text/html"

So test the MIME type with startswith()