Improve preg_replace

Add share button: Twitter, Facebook and Google+.

Fix class.

Add new config for author info.

Add author info on post.

Bugs fixes and improvements. Multi author fixed, post sort by date fixed
etc.

Fix posts shorting bugs due to multi author.

Add tag cloud widget and various style changes for better look.

Improving the profile page by adding posts list.

Change the aside style to position absolute to fix copyright notice.

This reverts commit d5e6973e82.

Previously the first post and last post generation code, hard coded
directly on main.html.php, now moved to functions.php.

Yay! HTMLy was born today.