Fix gaps in timeline when loading older after pressing show new

Fixes this:

1. Scroll any timeline until new posts are fetched a few times (try 10+)
2. Scroll back to the top and load new posts
3. The timeline will lose the older posts that were loaded
4. Next time you scroll down it'll start loading older posts pasts the time of point 1.

Most of the changes are from indents changing in the test, I only added 1 test without modifying others, and renamed/moved some describe/its

src/modules/statuses.js

@@ -333,6 +333,7 @@ export const mutations = {
     oldTimeline.newStatusCount = 0
     oldTimeline.visibleStatuses = slice(oldTimeline.statuses, 0, 50)
     oldTimeline.minVisibleId = last(oldTimeline.visibleStatuses).id
+    oldTimeline.minId = oldTimeline.minVisibleId
     oldTimeline.visibleStatusesObject = {}
     each(oldTimeline.visibleStatuses, (status) => { oldTimeline.visibleStatusesObject[status.id] = status })
   },