Also pass app object as parameter to configure callbacks (#698)

Author: daffl

lib/application.js

@@ -56,7 +56,7 @@ const application = {
   },
 
   configure (fn) {
-    fn.call(this);
+    fn.call(this, this);
 
     return this;
   },

test/application.test.js

@@ -65,6 +65,13 @@ describe('Feathers application', () => {
     });
   });
 
+  it('additionally passes `app` as .configure parameter (#558)', done => {
+    feathers().configure(function (app) {
+      assert.equal(this, app);
+      done();
+    });
+  });
+
   describe('Services', () => {
     it('calling .use with a non service object throws', () => {
       const app = feathers();