Ease symfony/validator version constraint slightly

Also fix a test
Merge pull request #912 from tommygnr/patch-1

Ease symfony/validator version constraint slightly
Update Vagrant and Puppet to work out of the box
Update installation instructions
Fixed most CS errors, with the notable exception to those regarding certain identifiers not being properly named.
Merge pull request #922 from boenrobot/cs-fix

PSR2 CS fixes