Added clickable #hashtags, @usernames and links. Seems to work okay, but further testing required.
Typo.
Added use of (and check for) the 'media' object (for image links), swapped out str_replace() for (case-insensitive) preg_replace(), some tidying.
Embedded image links now expand to clickable thumbnails (or not): default is on.
Merge pull request #20 from vaughany/master

Added clickable #hashtags, @usernames and links.