Websocket support proposal

To support this (https://github.com/hoisie/web/issues/105)

```go
func upgradeWebsocketHandler(wsHandler websocket.Handler) interface{} {
        return func(ctx *web.Context) {
                wsHandler.ServeHTTP(ctx.ResponseWriter, ctx.Request);
        }
}
```

Removed the interface type web.ResponseWriter and replaced with http.ResponseWriter