Keep tab bar shown (expanded) if one of triggers is still there. (#552)

The tab bar can be shown by three reasons: mouseover, keyboard shortcut,
and feedback for new tabs. However, sometimes two or more triggers can
be fired in a same time. Now TST keeps the tab bar showing (expanded)
for combinated cases, like: shown by the keyboard shortcut, the mouse
goes onto the tab bar, and it leaves from the tab bar.
Break lines after condition block of "if" statements
Allow users to create new subtree from partially selected tree of tabs (#553)
Support "hide tab bar only when one tab" again for Tab Mix Plus (#557)
Detect mode of Tab Mix Plus correctly
Fix indent
Disable detection for Tab Mix Plus because it is buggy for me.
Hide vertical tab bar in the DOM-fullscreen mode (ex. YouTube) (#564)
Merge branch 'master' into thintabs