Prevent the cursor from setting it to initial position in IE

Fixes #2028 and #2211.

The fix is based on [this comment](https://github.com/ivaynberg/select2/issues/2028#issuecomment-32418126).

Now the bug doesn't occur anymore as you can see here: http://mkurz.github.io/select2/select2-latest.html (Forked the gh-pages and provided the patched select2.js)