ci: remove .travis.yml file

Validate callback type (#10)

ci: switch to github actions (#11)

Run travis with PHP7 (#6)

Merge pull request #4 from stof/patch-1

Improve the composer instructions in the readme

Merge pull request #3 from pborreli/php-56

Removed hhvm allow_failures as it works

Added PHP 5.6 to travis-ci

Merge pull request #2 from GromNaN/static

Allows to call the `validate` method statically

Remove hhvm hack in travis' config

Update README.md

Add badges

Use simplified version of HHVM on Travis-CI