image: Prevent insertion of endless spaces.

Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>
button: Use [:alnum:] in url regex instead of ranges.

This should handle unicode characters in urls better.  Hey even
http://☃.net/ works now!  🙌

Signed-off-by: Rüdiger Sonderfeld <ruediger@c-plusplus.de>