Results send to Patchwork can now be marked as markdown (on a Test model
level). Such results are then rendered into HTML and displayed on the
web views.

Emails that are sent to the mailing list / recipients for such results
are going to be multipart/alternative containing both the text form (raw
Markdown) and the rendered HTML.

Fixes: #6


Signed-off-by: Arkadiusz Hiler <arkadiusz.hiler@intel.com>