Add Express

Express is a tool for creating websites faster by means
of Node.js and Javascript. It is the web-server software
that we're building on top of, akin to Apache or IIS.
Ignore 'node_modules'

The node_modules folder holds the libraries we're using
that we've installed through npm, or the Node Package
Manager. We don't need to keep these in our git repository,
as they're installed by Nodejitsu (our web host) when
we put our program up there.
Add initial home page

Add a basic home page for our site, with a
simple welcome message.