Update jquery.mb.browser.js

In new version of opera ( > 20 I think), the name in user agent was replaced by "OPR" instead of "Opera"
Merge pull request #5 from mrwhitesky/patch-1

Update jquery.mb.browser.js 
In new version of opera ( > 20 I think), the name in user agent was replaced by "OPR" instead of "Opera"