Removed TST API reliance, now it will work with TST and normal tabs.

Unfortunately, this means that the "middle click in tab bar to open most recently closed tab" feature no longer works. But good news: there is another addon named TST-MiddleClick that does exactly this! Check it out and make sure to thank its author.

Fixed registration bug, should register more reliably when opening Firefox and when Tree Style Tab updates. Fixed bug with the closed tabs list not updating sometimes. Changed wording of the list size option. Please see the options page for information on how to view more than 10 items in the recently closed list.

Minor update, fixes URL and icon.