Remove favicon and methodOverride middlewares

`methodOverride` is supposed to provide compatibility for older
"browsers" which aren't able to send XHR requests with proper HTTP
methods. Since the only thing talking to `lamassu-server` is the ATM, we
don't need this middleware.

`favicon` middleware is exactly what it sounds like.

lib/app.js

@@ -63,9 +63,7 @@ module.exports = function (options) {
   });
 
   app.use(express.logger());
-  app.use(express.favicon());
   app.use(express.bodyParser());
-  app.use(express.methodOverride());
 
   if (!options.https) {
     server = http.createServer(app);