Add json() method (#4)

* Added sendJSON function that will automatically stringify the json object for you

* rename `sendJSON` to `json`

* rewrite: use ws directly & remove return statement

Calls to `ws.send` don't return anything, so there's no need to return anything either~

Author: Marco Sparagna

src/index.js

@@ -32,5 +32,9 @@ export default function (url, opts) {
 		}, ms);
 	};
 
+	$.json = x => {
+		ws.send(JSON.stringify(x));
+	}
+
 	return $.open();
 }