add unit test, fix dev dependencies, add Makefile

spec/indexSpec.js

@@ -0,0 +1,24 @@
+"use strict";
+/* eslint-env jasmine */
+
+let express = require("express"),
+    request = require("supertest"),
+    bundle = require("../");
+
+describe("index", () => {
+    const app = express();
+    
+    app.use(bundle({
+        prefix: "hello"
+    }));
+
+    it("/metrics returns up=1", done => {
+        request(app)
+            .get("/metrics")
+            .end((err, res) => {
+                expect(res.status).toBe(200);
+                expect(res.text).toMatch(/hello:up\s1/);
+                done();
+            });
+    });
+});