Merge pull request #94 from bahamut1221/patch-1

Add possible option firefox binary

Author: everzet

src/Behat/MinkExtension/Extension.php

@@ -344,6 +344,7 @@ public function getConfig(ArrayNodeDefinition $builder)
                                                 thenInvalid('Cannot find profile zip file %s')->
                                             end()->
                                         end()->
+                                        scalarNode('binary')->end()->
                                     end()->
                                 end()->
                                 arrayNode('chrome')->