FF fix.

js/bundle.js

@@ -267,7 +267,7 @@
 	    fetch: function fetch(url) {
 	        return new Promise(function (resolve, reject) {
 	            var listener = function listener(_ref) {
-	                var req = _ref.srcElement;
+	                var req = _ref.target;
 
 	                req.status === 200 ? resolve(req.responseText) : reject("busted");
 	            };

js/index.js

@@ -200,7 +200,7 @@ const main = {
     },
 
     fetch: (url) => new Promise((resolve, reject) => {
-        const listener = ({ srcElement: req }) => {
+        const listener = ({ target: req }) => {
             req.status === 200 ? resolve(req.responseText) : reject("busted");
         };