update extensions doc (#563)

* fix trailing whitespace

* fix broken links and remove special handlers

docs/operating/extending.md

@@ -2,18 +2,24 @@
 
 IronFunctions is extensible so you can add custom functionality and extend the project without needing to modify the core.
 
-There are 4 different ways to extend the functionality of IronFunctions. 
+There are multiple ways to extend the functionality of IronFunctions.
 
 1. Listeners - listen to API events such as a route getting updated and react accordingly.
 1. Middleware - a chain of middleware is executed before an API handler is called.
-1. Add API Endpoints - extend the default IronFunctions API. 
+1. Add API Endpoints - extend the default IronFunctions API.
-1. Special Handlers - TODO: DO WE NEED THIS ANYMORE??
 
 ## Listeners
 
-Listeners are the main way to extend IronFunctions. 
+Listeners are the main way to extend IronFunctions.
 
-You can easily use listeners basically creating a struct with [valid methods](#Listener Requirements) and adding it to the `IronFunctions API`.
+The following listener types are supported:
+
+* App Listeners - [GoDoc](https://godoc.org/github.com/iron-io/functions/api/server#AppListener)
+* Runner Listeners - [GoDoc](https://godoc.org/github.com/iron-io/functions/api/server#RunnerListener)
+
+### Creating a Listener
+
+You can easily use app and runner listeners by creating a struct with valid methods satisfying the interface for the respective listener and adding it to the IronFunctions API
 
 Example:
 
@@ -42,68 +48,25 @@ function main () {
     srv := server.New(/* Here all required parameters to initialize the server */)
 
     srv.AddAppListener(myCustomListener)
-    
+
     srv.Run()
 }
 ```
 
-### Creating a Listener
-
-These are all available listeners:
-
-#### App Listeners
-
-See the godoc for AppListener [in this file](/iron-io/functions/blob/master/api/server/apps_listeners.go)
-
-#### Runner Listeners
-
-See the godoc for RunnerListner [in this file](/iron-io/functions/blob/master/api/server/runner_listeners.go).
-
-## Adding API Endpoints
-
-You can add API endpoints by using the `AddEndpoint` and `AddEndpointFunc` methods to the IronFunctions server. 
-
-See examples of this in [/examples/extensions/main.go](/examples/extensions/main.go). 
-
 ## Middleware
 
 Middleware enables you to add functionality to every API request. For every request, the chain of Middleware will be called
-in order allowing you to modify or reject requests, as well as write output and cancel the chain.
+in order, allowing you to modify or reject requests, as well as write output and cancel the chain.
 
 NOTES:
 
 * middleware is responsible for writing output if it's going to cancel the chain.
 * cancel the chain by returning an error from your Middleware's Serve method.
 
-See examples of this in [/examples/Middleware/main.go](/examples/middleware/main.go).
+See examples of this in [examples/middleware/main.go](../../examples/middleware/main.go).
 
-## Special Handlers
+## Adding API Endpoints
 
-To understand how **Special Handlers** works you need to understand what are **Special Routes**.
+You can add API endpoints to the IronFunctions server by using the `AddEndpoint` and `AddEndpointFunc` methods.
 
-**Special Routes** are routes that doesn't match any other API route. 
+See examples of this in [examples/extensions/main.go](../../examples/extensions/main.go).
-
-With **Special Handlers** you can change the behavior of special routes in order to define which function is going to be executed.
-
-For example, let's use special handlers to define `mydomain` as the `appname` for any request for `mydomain.com`.
-
-```
-type SpecialHandler struct{}
-
-func (h *SpecialHandler) Handle(c server.HandlerContext) error {
-    host := c.Request().Host
-    if host == "mydomain.com" {
-        c.Set("app", "mydomain")
-    }
-}
-
-func main () {
-    sh := &SpecialHandler{}
-
-    srv := server.New(/* Here all required parameters to initialize the server */)
-    srv.AddSpecialHandler(sh)
-    srv.Run()
-}
-``` 
-
-With the code above, a request to `http://mydomain.com/hello` will trigger the function `/mydomain/hello`