Some fixes for release 1.6

MRs: #158 & #157

Symfony 4 ready

Thanks to @pesektomas now it is compatible with Symfony 4!

Fix problem with "fp_js_validator.js"

Aassetic added as required dependency which will combine all JS files in one fp_js_validator.js automatically

Release for Symfony 3.1 & 3.2

1.5

Remove 3.3 because of not solved dependencies

Freeze on Symfony 3.0.*

1.4.* will work only with Symfony 3.0.* because of symfony/symfony#20284

First release for Symfony 3.0

Thanks to @maryo for PR #105 now it works with Symfony 3.0! :)

First release for Symfony 2.7.* & 2.8.*

Thanks to @maryo for PR #106 now it works with Symfony 2.7 and 2.8! :)

Updated 1.2 to support Symfony up to 2.7

PR #104
Updated Symfony constraint to <2.7
Added Symfony 2.6 to travis configuration
Support for IsFalse/IsTrue/IsNull
Testcase of multiplechoice made less strict so changes after 2.5 dont fail
valid filename of generated screenshot on Windows

Fixed validation_groups when option is a Closure

Merge pull request #99 from 66Ton99/eko

Fixed validation_groups when option is a Closure #93

Fixed travis build & some improvements

Merge pull request #97 from 66Ton99/1.2

[1.2] Fixed travis build & some improvements