Adding documentation to the README file as per issue jaredhanson#7

Taken augmented functions documentations from the [authentication middleware](https://github.com/jaredhanson/passport/blob/5334ee0fa52ab5f5225ddee695697432e0565679/lib/middleware/authenticate.js#L178) to describe the augmented methods as per issue jaredhanson#7

README.md

@@ -47,6 +47,96 @@ CustomStrategy.prototype.authenticate = function(req, options) {
 }
 ```
 
+#### Augmented Methods
+The Strategy.authenticate method is called on an instance of this Strategy that's augmented with the following action functions.  
+These action functions are bound via closure the the request/response pair.  
+The end goal of the strategy is to invoke *one* of these action methods, in
+order to indicate successful or failed authentication, redirect to a
+third-party identity provider, etc.
+
+* [.success(user, info)](#Strategy+success)
+* [.fail(challenge, status)](#Strategy+fail)
+* [.redirect(url, status)](#Strategy+redirect)
+* [.pass()](#Strategy+pass)
+* [.error(err)](#Strategy+error)
+
+
+##### strategy.success(user, info)
+Authenticate `user`, with optional `info`.
+
+Strategies should call this function to successfully authenticate a
+user.  `user` should be an object supplied by the application after it
+has been given an opportunity to verify credentials.  `info` is an
+optional argument containing additional user information.  This is
+useful for third-party authentication strategies to pass profile
+details.
+
+**Kind**: instance method of [Strategy](#Strategy)  
+**Api**: public  
+
+| Param | Type |
+| --- | --- |
+| user | Object | 
+| info | Object | 
+
+
+##### strategy.fail(challenge, status)
+Fail authentication, with optional `challenge` and `status`, defaulting
+to 401.
+
+Strategies should call this function to fail an authentication attempt.
+
+**Kind**: instance method of [Strategy](#Strategy)  
+**Api**: public  
+
+| Param | Type |
+| --- | --- |
+| challenge | String | 
+| status | Number | 
+
+
+
+##### strategy.redirect(url, status)
+Redirect to `url` with optional `status`, defaulting to 302.
+
+Strategies should call this function to redirect the user (via their
+user agent) to a third-party website for authentication.
+
+**Kind**: instance method of [Strategy](#Strategy)  
+**Api**: public  
+
+| Param | Type |
+| --- | --- |
+| url | String | 
+| status | Number | 
+
+
+##### strategy.pass()
+Pass without making a success or fail decision.
+
+Under most circumstances, Strategies should not need to call this
+function.  It exists primarily to allow previous authentication state
+to be restored, for example from an HTTP session.
+
+**Kind**: instance method of [Strategy](#Strategy)  
+**Api**: public  
+
+##### strategy.error(err)
+Internal error while performing authentication.
+
+Strategies should call this function when an internal error occurs
+during the process of performing authentication; for example, if the
+user directory is not available.
+
+**Kind**: instance method of [Strategy](#Strategy)  
+**Api**: public  
+
+| Param | Type |
+| --- | --- |
+| err | Error | 
+
+
+
 ## Related Modules
 
 - [chai-passport-strategy](https://github.com/jaredhanson/chai-passport-strategy) — helpers for testing strategies with the Chai assertion library