Clean up stream base a bit
Remove unnecessary param, it's the default
Add backfill method to tweets modellist

Useful for getting old tweets and preventing weird timeline reshuffling
when a list is on-demand loaded but has had updates already.
Fix tweet sorting, overwrote the wrong fn name
Clean up calling of tweets.backfill
Insert tweets at the end of the existing list
Merge pull request #44 from tivac/fix-timeline-loading-behavior

Fix timeline loading behavior