* Externalize negotiate

* Install pecl-krb5

We need to include this in our travis-tests as long as we include the negotiate-module in the release

* Update Psalm

* Ignore DocblockTypeContradiction and RedundantConditionGivenDocblockType

* Fix Psalm-errors

* Raise minimum PHP-version to 5.6

* Update lock-file accordingly

* Fix phpunit

* Suppress Psalm-issue

HHVM is not compatible with Symfony4 and it is no longer worth the hassle

Closes #628

Ignore closure return types, as we need to support PHP < 7.

This is not really workable. Need to devise another way to run psalm
periodically without keeping it breaking the build.

This prevents a lot of -dev dependencies in composer.lock which are
not used otherwise and generate 'scary' warnings like "Package x is
abandoned".

Closes #718

We've just been moved from Precise to Trusty, and PHP 5.3 is not available in the latter, so builds fail.

The segfault happens in the coverage report. Since we send coverage
info only with PHP 5.6, avoid running it entirely, saves buildtime aswell.

Try to make it build with the saml module included by using the phpunit version we are requiring instead of the one preinstalled.

Calling composer with "update" instead of "install" should update the versions referenced in the composer.lock file, instead of blindly trying to install them, leading to conflicts.

Try with "composer update" instead of "composer install". The latter does not support --prefer-lowest.