Update PHPUnit to its enw major version
minor #955 Update PHPUnit to its new major version (stof)

This PR was merged into the 2.0.x-dev branch.

Discussion
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Update PHPUnit to its new major version

4.0 and 4.1 would not be allowed by the ``~3.7`` constraint

Commits
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639f213 Update PHPUnit to its enw major version