changed 'expect' to 'except' where appropriate in docs

Documentation read, "It would respond with master page html for any request, expect the requests for..." but I'm pretty sure it should read, "It would respond with master page html for any request, except the requests for..."

So I changed it to "except" so it makes more sense.

related issue: https://github.com/alexanderbeletsky/backbone-express-spa/issues/23