Enabled users to unselect items

Users can unselect selected backlog items again
by pressing on a blank part of the page.
Fixes after review

* Made sure the header can be pressed to unselect as well
* Optimized traversing of the document for selected items
Merge pull request #118 from fredrikpersson/unselect

Enabled users to unselect items
Updated version number to 1.2.2
Merge pull request #120 from fredrikpersson/master

Updated version number to 1.2.2
Merge remote-tracking branch 'upstream/master' into data-push