Add tests for RoomList

[lukebarnard1]

• Move waitForUpdate (this wasn't necessary in the end)
• Install lolex for clock mocking (this is what sinon uses under the hood but using the most recent version directly seemed better)
• Add tests for optimistic updates in moving room tiles (two tests skipped: dragging from people to rooms is glitchy because the optimistic update doesn't work)
• Add tests for testing that the room list updates when group data is loaded with new rooms added

Added test output:

 RoomList
    when no tags are selected
      does correct optimistic update when dragging from
        ✓ rooms to people (33ms)
        ✓ rooms to favourites (23ms)
        ✓ rooms to low priority (26ms)
        - people to rooms (0ms)
        ... (all others pass)
    when tags are selected
      ✓ displays the correct rooms when the groups rooms are changed (11ms)
      does correct optimistic update when dragging from
        ✓ rooms to people (16ms)
        ✓ rooms to favourites (15ms)
        ✓ rooms to low priority (15ms)
        - people to rooms (0ms)
        ... (all others pass)

[dbkr]

otherwise lgtm!

[dbkr]

Probably a bit moot in this case, but in general for unit tests where nothing is stored between runs, I would probably use the same data each time to make them completely deterministic.

[lukebarnard1]

IRL we discussed and decided that it's ok to do this for room IDs (as here we simulate a homeserver randomly generating unique IDs and the app should be totally ambivalent to the content of the IDs)