travis: PHP 5.6 added
travis: PHP 5.6 added

KnpLabs/DoctrineBehaviors,j-ledoux/DoctrineBehaviors,ksom/DoctrineBehaviors,shieldo/DoctrineBehaviors,mediahost/DoctrineBehaviors,lemoinem/DoctrineBehaviors,MAXakaWIZARD/DoctrineBehaviors,digitalkaoz/DoctrineBehaviors,DerekRoth/DoctrineBehaviors,MakG10/DoctrineBehaviors,nick4fake/DoctrineBehaviors,vba-ds/DoctrineBehaviors,bocharsky-bw/DoctrineBehaviors