Fixed problem where the add_post_link method would truncate the status update in the middle of a link. This led to sending Twitter broken links.

Refactored :extract_truncated_link method

Removed complicated while loop in avoiding cutting off links, using refactoring from MrZYX
Merge pull request #4384 from andrewcsmith/bug/4211-twitter-should-not-cut-links

Fixed problem where the add_post_link method would truncate the status update in the middle of a link