Documentation step ordering, regarding creating new clients

[joshavant]

As a new user of rack-oauth2-server, I wanted to propose moving step 5 to step 3, and moving the rest of the steps down, accordingly.

Trying to get this going for the first time, my go-to sanity checks of if I'm doing it right are:
-setup the script
-setup a client
-attempt to get an authorization token

But, illogically, the document is laid out:
-setup the script
-how to get an authorization token
-...
-setup a client

A reordering seems most logical and easy to follow, for new users.

Thanks for the awesome gem!