few changes

Hi, found this extension to almost suit my needs. I made few changes that improve the UI (in my point of view:) and added a function to 'move' the tabs to bookmarks (i.e. close the tabs after bookmarking them).

My use case is - take a crowded browser window, ctrl-click to select all tabs that are related to one 'research topic', and move them all to a bookmark folder, when I decide to postpone that particular research topic. The benefit is that they're synced to all my other computers.

I also felt that the background page was not needed for the functionality, so I removed it, which makes the plugin even more lightweight.