[Minor] jsDoc comment fixed
[Fix] Minor fix: check is CUs specifier is specified in the urlData before calling `updateCUsAndRelatedState` upon tab activation.

Plus, reduce waiting time upon tab activation before assuming its actually being activated
[Fix] Added missing check
[Fix] It's useful to not reset $lastSelectedCU (which happens when there is a url change). Closes #55

(Often when you click on a link to the shared content on a CU, like a photo shared in FB,
it opens in a modal window, while changing th URl at the same time. When we click outside
or press 'esc' to get back to the main feed, this fix ensures that the previously selected
CU is selected.)