docs: remove references to express's old app.configure() method

[andrewagain]

app.configure() has been removed from the latest version of express.

StackOverflow post:
http://stackoverflow.com/questions/18637148/using-app-configure-in-express

Github issue:
expressjs/express#936

Error if you try to use app.configure with express 4:

11:16:32 web.1  | app.configure(function() {
11:16:32 web.1  |     ^
11:16:32 web.1  | TypeError: Object function (req, res, next) {
11:16:32 web.1  |     app.handle(req, res, next);
11:16:32 web.1  |   } has no method 'configure'

[coveralls]

Coverage remained the same at 100.0% when pulling dfcaaac on ahfarmer:master into d0f6b6c on jaredhanson:master.