Use jquery.sceditor.mybb.css from plugin sceditor for Mybb

jquery.sceditor.mybb.css from https://github.com/samclarke/SCEditor-MyBB/tree/master/jscripts/sceditor

Better use jquery.sceditor.mybb.css instead jquery.sceditor.default.min.css has better style for blockquote, blockcode etc..

jquery.sceditor.mybb.css
http://i.imgur.com/V7u7TiE.png

jquery.sceditor.default.min.css
http://i.imgur.com/hZUOtKZ.png

And i don´t recommend minify file in this case, because this file is used too to put style for pre tag (used in spoiler tag) etc. Simply put this file is often used for customization.

This pull fix too #667 #666 #662 #663 . So case to apply this, does not apply to others.