CiviContribute widget fails to render in WordPress

WordPress users are reporting that the CiviContribute widget fails to render when they paste it into a post or page. See:
http://forum.civicrm.org/index.php/topic,33965.0.html

I have confirmed that this is the case and the reason is that WordPress applies `wp_autop()` formatting to the content of the post/page - including the widget code - thus inserting paragraph tags where they kill the execution of the javascript and mess with the CSS declarations.

I am opening a PR that removes the blank lines from the Widget.php template which should solve the most immediate problem. There are further issues related to switching to the TinyMCE editor and WordPress multisite - they would both be solved by implementing a native WordPress widget.