Reworked to use the native collapse functionality in Trello. This should reduce the issues that could arise from the prior kludges.

More bug-fixes:
- remove floating text near collapsed lanes
- apply collapse/uncollapse when filtering (no need to wave your mouse over lanes any more)
- uncollapse when adding a new card, collapse again if cancelling and collapseable

Fixes for the new Trello UI which completely broke this extension

Only update is to broaden the target url for this addon.
Originally, I'd only seen boards at trello.com/b/{board}, and wanted to keep permissions to a minimum, but recently someone linked me to trello.com/c/{board}. This update sets the extension active on all of trello.com.

minor update: better UX when uncollapsing a lane - the lane used to stretch out to full window height, with a skinny card, and then come right. By temporarily hiding cards in collapsed lanes and unhiding them on the next tick after uncollapsing a lane, a smoother transition is achieved.