Keyboard shortcuts to select/switch tab

Hi Patrik

Thanks for your extension. I like it but wanted to be able to select a tab entirely with the keyboard so wrote this code if you want to use it. 

The addition numbers the search matches when using the search input and the desired tab can be immediately switched to by hitting its number key instead of using the mouse.

For anyone wanting to use this I recommend setting up a keyboard shortcut in the extensions page to open Tab Manager too (As @denilsonsa described: Go to Settings → Extensions → Scroll to the bottom → Configure commands)
I use Ctrl-Q as the release of Ctrl key causes all tabs to be selected and numbered and this aligns well with Chrome's built in tab switching shortcuts (ctrl + number key).

Re Issue #16