Files now include  ...vendor/autoload.php where needed and the
external_dependencies folder has been removed. The installation instructions
have been updated to reflect these changes. nixtape and gnukebox have separate
composer files to ease separate installation.
Feedback on this strategy is welcomed.

Use phpunit rather than simpletest for all tests. simpletest is no longer a
dependency.

Update to current versions of libraries. Where this has caused errors to be
logged (notably for templates) code has been changed to resolve them.