Prevent IE 11 from using document.selection

For IE 11, document.selection is no longer supported. See 
http://msdn.microsoft.com/en-us/library/ie/ms535869(v=vs.85).aspx 
for details. 

Updated condition so IE 11 uses selectionStart and 
selectionEnd similar to Chrome and Firefox.

Versions of IE < 11 are unaffected.

![image](https://f.cloud.github.com/assets/516155/2479788/b093e6ec-b0a2-11e3-810a-1a395c515226.png)