Add twitteroauth library into the repository

This commit adds the twitteroauth PHP library to the repository's code, so
installers of the extension no longer need to download the needed files
themselves, and it's more appropriate for the files to be here rather than the
MediaWiki includes folder.  Links and license files have been included to
fulfill the terms of the license twitteroauth is distributed under.

Unfortunately, it was impractical to include the library as a git submodule,
as most of the repository was unnecessary.  The files were instead simply
copied into /includes, and will need to be manually updated as needed.

Patchsets 2 and 3 removes some whitespacing errors (trailing whitespace and
ends-of-lines).

Change-Id: I6d25b511b637a4cf96d4caca11a1b9d4150f101e