[bug 869455] HTML email for announcements
[bug 869453] HTML email for private messages
Add six

This is a requirement of pyelasticsearch 0.5 which added support for
Python 3.
Update pyelasticsearch to 0.5

This picks up the settings API stuff which we'll use at some point.
[bug 838638] Add SearchMappingTypes and rework indexing (1/2)

This adds a parallel universe of indexing which the es_reindex_cmd
and admin code will use to create the new index with the new
SearchMappingType code.

It also adds a bunch of TODO lines for things that need to be fixed
in the subsequent commit.

Comments out one test that gets whiny with the parallel indexing
worlds.
[bug 838638] Update views for new mapping types (2/2)

This updates everything to use the new mapping types and ditching the
old unified doctype.