Disable backing up globals in PHPUnit

This is a Bad Thing as it interferes with test isolation, but since TWFY
is so reliant on globals doing interesting things it is the only way to
make the *current* codebase testable in any kind of depth.

Eventually this should go away.
Add memcached as a service on Travis.
Add PHP 5.6 as a tested version in Travis
Improvements to Travis behaviour

* Don't download composer.phar, it's already in the repository.
* We no longer support short opening tags.
* Sending data to Scrutinizer should happen only on target version (5.4)
Ignore PHP errors during testing so that we can actually ship something.

This is a Bad Thing and we need to try remove deprecation warnings ASAP
so we can turn this back off.
Merge branch 'testing-improvements'