Merge pull request #9 from dpolivy/master

Add support for upper and mixed-case bbcode tags
version bump

Signed-off-by: Nick Campbell <nicholas.j.campbell@gmail.com>
added center tag

<center></center> is deprecated in HTML5, but as many BBCode files use this tag frequently it should be supported. Replacing [center[[/center] with something else like <p style='text-aligin: center'></p> looks like an overkill for me.
Merge pull request #10 from ronny332/master

center tag