fix(package): update mysql2 to version 2.1.0

Closes #31

Author: greenkeeper[bot]

package.json

@@ -34,7 +34,7 @@
     "http-errors": "~1.7.0",
     "jade": "~1.11.0",
     "morgan": "~1.9.0",
-    "mysql2": "^1.6.1",
+    "mysql2": "^2.1.0",
     "prettier": "^1.14.2",
     "pretty-quick": "^1.6.0",
     "sequelize": "^4.38.0",