Update library/extensions/comments-extensions.php

Changed type="text" to type="email" for the email input.
Changed type="text" to type="url" for the web address.
These HTML5 attributes are 100% backwards compatible and revert to type="text" for older browsers which ignore these input types.
Some info on the types here: http://diveintohtml5.info/forms.html
Merge pull request #18 from coliff/patch-1

Update library/extensions/comments-extensions.php