Add created_at and created_by columns to series_sales table and fill them with default values.

Author: cssru

.travis.yml

@@ -12,9 +12,9 @@ sudo: required
 addons:
   apt:
     packages:
-    - mysql-server-5.6
-    - mysql-client-core-5.6
-    - mysql-client-5.6
+    - mysql-server-5.7
+    - mysql-client-core-5.7
+    - mysql-client-5.7
 
 before_script:
   - if [ "$SPRING_PROFILES_ACTIVE" = 'travis' ]; then