fix(package): update nodemailer to version 6.4.8

Closes #28

Author: greenkeeper[bot]

package.json

@@ -33,7 +33,7 @@
     "moment-duration-format": "^2.2.2",
     "morgan": "^1.9.1",
     "multiparty": "^4.2.0",
-    "nodemailer": "~6.2.1",
+    "nodemailer": "~6.4.8",
     "nodemailer-mock-transport": "^1.3.0",
     "passport": "~0.4.0",
     "passport-local": "~1.0.0",