utf8 to utf8mb4
http://ashleyangell.com/2014/04/mysqls-utf8-isnt-really-utf8-and-how-to-properly-support-unicode/
http://mathiasbynens.be/notes/mysql-utf8mb4
# For each database:
ALTER DATABASE database_name CHARACTER SET = utf8mb4 COLLATE = utf8mb4_unicode_ci;
# For each table:
ALTER TABLE table_name CONVERT TO CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
# For each column:
ALTER TABLE table_name CHANGE column_name column_name VARCHAR(191) CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
# (Don’t blindly copy-paste this! The exact statement depends on the column type, maximum length, and other properties. The above line is just an example for a `VARCHAR` column.)
