Don't test vobject anymore in this branch.
Testing with --prefer-lowest.
We must use composer update, instead of composer install for this.
PHP 5.6 is not allowed to fail.
Added --prefer-source
Merge branch '1.7' into 1.8

Conflicts:
	.travis.yml
Hoping these work.
Revert "Hoping these work."

This reverts commit ed2e7fe13dc8433c30c9850aed5e1bd268c074a3.
double env: key.
Merge branch '1.8' into 2.0

Conflicts:
	.travis.yml
	tests/phpunit.xml
When we are testing the oldest version of dependencies, we don't care
about *their* unittests.
Corrected path.
Merge branch '2.0' into 2.1

Conflicts:
	.travis.yml