Add closeTabsToLeft, closeTabsToRight and closeOtherTabs commands
Merge pull request #1129 from mrmr1993/closeOtherTabs

Add closeTabsToLeft, closeTabsToRight and closeOtherTabs commands
Only block keyup for keys where we have handled a keyup/press event

Fixes the issue of Vimium indiscriminately capturing keyup events,
introduced in PR #978.