Use mysql 5.7 with disabled option ONLY_FULL_GROUP_BY (which causes many problem to people)

mysql/Dockerfile

@@ -1,4 +1,4 @@
-FROM mysql:5.6
+FROM mysql:5.7
 
 MAINTAINER Mahmoud Zalt <mahmoud@zalt.me>
 

mysql/my.cnf

@@ -4,3 +4,6 @@
 # http://dev.mysql.com/doc/mysql/en/server-system-variables.html
 
 [mysql]
+
+[mysqld]
+sql-mode="STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION"