path ignored for unversioned files

[benmccann]

I include staticify like this:

const staticify = require('staticify')(path.join(__dirname, 'public'), { pathPrefix: '/public' });
app.use('/public', staticify.middleware);

This works when I receive requests for versioned files, but not if I request the file without including the hash

I can work around the issue using the code below, but it'd be nice if staticify.middleware did this for me

    if (!isProd) {    
        app.use(function(req, res, next) {
            if (req.url.startsWith('/javascripts') || req.url.startsWith('/css')) {
                req.url = '/public/' + req.url;
            }
            next();
        });
    }

[XhmikosR]

If you make a PR with tests, someone will be able to review it :)