MySQL 5.6: explicit_defaults_for_timestamp
I had the same problem, tried to change the sql_mode but didn't work, then changed the explicit_defaults_for_timestamp to 0 and worked!!!, but I encourage you to read the following to understand the issue:
http://openbedrock.blogspot.mx/2015/04/what-happened-to-mysql-timestamp-columns.html
and
https://dev.mysql.com/doc/refman/5.7/en/sql-mode.html