Fix errors when including libraries and unnecessary warnings when foreach'ing $ctAliases

These three commits fix two errors I encountered when installing this extension, the first and most breaking one is that the extension doesn't know where to look to find the twitteroauth.php library because the full path to the MediaWiki include directory is not defined.  This is fixed in this pull request.

In addition, this pull requests adds checking if $ctAliases is empty before attempting to foreach it, suppressing many unnecessary PHP warnings and probably saving a tad bit of CPU time.