As of 28770a5143bb5b48389d5ad4ce235625c12f1056 we no longer need this
file as the server should now be started with `ruby app.rb` instead of
`rackup`.

Template that displays when the user is logged in.

Adjust the login test to check for the text in this template.

Move boilerplate code from `index.erb` into `layout.erb` to allow us to
use it in additional templates.

Create a couple new methods to extract login functionality and remove
duplicate test code.

So that the characters get masked.

When logging in with unrecognised credentials, the response should
include "Unrecognized user".

When logging in with the correct credentials, set a session variable and
redirect to the login page. Custom display for a user who is logged in.

Add a logout method to delete the session variable, thus logging out the
user.

Use Rack's built-in session cookies to facilitate session management.

Don't wrap our routes/controllers in a `Sinatra::Base` class to keep
things simple. Was doing this because I thought I needed to in order to
be able to tell Capybara where the application was but looking at the
Sinatra testing page (http://www.sinatrarb.com/testing.html), they
provide an example for Capybara that details this
`Sinatra::Application.new` call that I can make instead. This frees us
up to use the simplified application definition.

Saw this on the Sinatra testing page
(http://www.sinatrarb.com/testing.html). Seems like I should put it in
to be a good Rack citizen.