Feature/websockets (#273)

* #212 - hacked websockets proxy together

* faffing around

* #212 hacking away :(

* #212 websockets proxy middleware working

* #212 map when for webockets working

* #212 some test refactor

* #212 temp commit

* #212 websockets proxy working, tests passing...need to do some tidying and write docs

* #212 more code coverage

* #212 docs for websockets

* #212 updated readme

* #212 tidying up after websockets refactoring

* #212 tidying up after websockets refactoring

* #212 tidying up after websockets refactoring

* stuck a warning in about logging levels into docs!

docs/features/websockets.rst

@@ -0,0 +1,68 @@
+Websockets
+==========
+
+Ocelot supports proxying websockets with some extra bits. This functionality was requested in `Issue 212 <https://github.com/ThreeMammals/Ocelot/issues/212>`_. 
+
+In order to get websocket proxying working with Ocelot you need to do the following.
+
+In your Configure method you need to tell your application to use WebSockets.
+
+.. code-block:: csharp
+
+     Configure(app =>
+    {
+        app.UseWebSockets();
+        app.UseOcelot().Wait();
+    })
+
+Then in your configuration.json add the following to proxy a ReRoute using websockets.
+
+.. code-block:: json
+
+       {
+            "DownstreamPathTemplate": "/ws",
+            "UpstreamPathTemplate": "/",
+            "DownstreamScheme": "ws",
+            "DownstreamHostAndPorts": [
+                {
+                    "Host": "localhost",
+                    "Port": 5001
+                }
+            ],
+        }
+
+With this configuration set Ocelot will match any websocket traffic that comes in on / and proxy it to localhost:5001/ws. To make this clearer
+Ocelot will receive messages from the upstream client, proxy these to the downstream service, receive messages from the downstream service and 
+proxy these to the upstream client.
+
+Supported
+^^^^^^^^^
+
+1. Load Balancer
+2. Routing
+3. Service Discovery
+
+This means that you can set up your downstream services running websockets and either have multiple DownstreamHostAndPorts in your ReRoute 
+config or hook your ReRoute into a service discovery provider and then load balance requests...Which I think is pretty cool :)
+
+Not Supported
+^^^^^^^^^^^^^
+
+Unfortunately a lot of Ocelot's features are non websocket specific such as header and http client stuff. I've listed what won't work below.
+
+1. Tracing
+2. RequestId
+3. Request Aggregation
+4. Rate Limiting
+5. Quality of Service
+6. Middleware Injection
+7. Header Transformation
+8. Delegating Handlers
+9. Claims Transformation
+10. Caching
+11. Authentication - If anyone requests it we might be able to do something with basic authentication.
+12. Authorisation
+
+I'm not 100% sure what will happen with this feature when it get's into the wild so please make sure you test thoroughly! 
+
+