support environment variable inside behat.yml
support environment variable inside behat.yml

With symfony#21460 fixed (>= 3.3.0, symfony/symfony@a3fd5122), this change allow the use of environment variables in any section of behat configuration file.
For example: `base_url: "http://%env(HOSTNAME)%"`
Behat/Behat,spolischook/behat,spolischook/behat,spolischook/behat,Taluu/Behat