Fix 'bootstrap popover falls off page if editable is too close to window edge'

Fix 'bootstrap popover falls off page if editable is too close to window edge'.


Reference:
    https://github.com/twitter/bootstrap/pull/6713
    https://github.com/twitter/bootstrap/issues/7399
    https://gist.github.com/nonumber/5257443
comments
Merge branch 'patch-1' of git://github.com/belerweb/x-editable into belerweb-patch-1