fix(package): update mysql2 to version 2.1.0

Closes #72

Author: greenkeeper[bot]

package.json

@@ -46,7 +46,7 @@
     "ioredis": "latest",
     "lodash.omit": "^4.5.0",
     "mysql": "^2.16.0",
-    "mysql2": "^1.6.1",
+    "mysql2": "^2.1.0",
     "nodemailer": "^4.6.8",
     "nodemailer-mailgun-transport": "^1.4.0",
     "nodemailer-mock-transport": "^1.3.0",