HTML5/HTML fixes

In sidebar.html.twig:
1. Unwrapped "<p>There are no tags</p>" at the "Tag Cloud" section as p tags cannot be nested: http://stackoverflow.com/a/9852381/372654
2. Removed the redundant </p> at the "Latest Comments" section
Merge pull request #35 from halilim/patch-1

HTML5/HTML fixes