mysql: Use utf8mb4 character set

migrations/20170414193114-database-utf8mb4.js

@@ -0,0 +1,14 @@
+'use strict';
+
+var url = require('url');
+
+exports.up = function(db, callback) {
+    var dbName = url.parse(process.env.DATABASE_URL).path.substr(1); // remove slash
+
+    // by default, mysql collates case insensitively. 'utf8_general_cs' is not available
+    db.runSql('ALTER DATABASE ' + dbName + '  DEFAULT CHARACTER SET=utf8mb4 DEFAULT COLLATE utf8mb4_unicode_ci', callback);
+};
+
+exports.down = function(db, callback) {
+    callback();
+};