Move mongoUrl to src/vendor

And add a README to src/vendor

src/vendor/README.md

@@ -0,0 +1,8 @@
+# mongoUrl
+
+A fork of node's `url` module, with the modification that commas and colons are 
+allowed in hostnames. While this results in a slightly incorrect parsed result, 
+as the hostname field for a mongodb should be an array of replica sets, it's 
+good enough to let us pull out and escape the auth portion of the URL.
+
+See also: https://github.com/ParsePlatform/parse-server/pull/986