v2.0.0-beta6

Changelog

• Updating Graylog server version (2.3.0-rc.2-2 -> 2.3.0-1) #16
• Updating Composer version (1.1.2 -> 1.5.0) #17
• Updating phpredis version (3.1.2 -> 3.1.3) #18
• Updating RabbitMQ version (3.6 -> 3.6.10) #20
• Updating Redis version (3.2 -> 3.2.10) #21
• Minor refactoring of APCU version in Toolbox and PHP-FPM Dockerfiles #22
• Adding PHP Coding Standards Fixer #19
• Updating README.md