implement this.fetch (#178)

test/app/routes/credentials/index.html

@@ -0,0 +1,12 @@
+<h1>{{message}}</h1>
+
+<script>
+	export default {
+		preload({ query }) {
+			console.log(`here ${this.fetch}`);
+			return this.fetch(`credentials/test.json`, {
+				credentials: query.creds
+			}).then(r => r.json());
+		}
+	};
+</script>