Rewrite regex in getTabs() in readme.html to work on IE 11. Fixes #1797

This fixes the navigation menu bar of `readme.html` on Internet Explorer 11 (and hopefully down to IE 9). 

Tested on these fine browsers:

 - Google Chrome 38.0.2125.111 :heavy_check_mark:
 - Iceweasel 31.2.0 :heavy_check_mark:
 - Internet Explorer 8.0 (Windows XP SP3) :x:
 - Internet Explorer 11.0 (Windows 7 SP1) :heavy_check_mark:
 - Internet Explorer 11.0 (Windows 8.1) :heavy_check_mark:
 - midori 0.5.8 :heavy_check_mark:
 - Mozilla Firefox 33.0 :heavy_check_mark:
 - Opera 12.16 :heavy_check_mark: