groups pages WIP
most of the work for #1563
added missing files for #1563
fixed tests, and added getSortedSetUnion method to redis db, added test for new redis method
added getSortedSetRevUnion... just because.
finished up group list and group details pages - closed #1563
Merge remote-tracking branch 'origin/master' into groups-pages

Conflicts:
	src/topics/tags.js