Fixes #622.
Microsoft removed MSIE string from the UA of IE11, so jQuery.browser
detect now fails to recognize IE11 as IE. It is detected as Mozilla.
That's why player is not working in IE11 if preload="none" attribute is
set.
Merge pull request #638 from ZoranJambor/bug/622

Fixes #622.
Respect zero value for bufferTime config

bufferTime might be 0, so this option cannot be updated on a boulean
basis.