This is what i did for rendering html files. And it solved the errors. Install consolidate and mustache by executing the below command in your project folder.
$ sudo npm install consolidate mustache --save
And make the following changes to your app.js file
var engine = require('consolidate');
app.set('views', __dirname + '/views');
app.engine('html', engine.mustache);
app.set('view engine', 'html');
And now html pages will be rendered properly.