Update documentation to reflect --stdio flag deprecation (#2439)

doc/Using-Omnisharp.md

@@ -7,16 +7,16 @@ OnmiSharp requires a fully functioning .NET Core SDK installed and available fro
 This document is a rough overview of how to interact with OmniSharp, and what the various features are.
 
 ## Interfaces
-OmniSharp supports several interfaces over the command line.
+OmniSharp supports several interfaces over the command line. Depending on the interface, you need to use the corresponding package (see [Downloading OmniSharp](https://github.com/OmniSharp/omnisharp-roslyn/blob/master/README.md#downloading-omnisharp) for more info).
 
-1. Http
+1. Http (using the `omnisharp.http` package)
   The http interface allows you to start up the server and communicate with it over HTTP.  This interface is pull based, so the server has no way to push information to the client.  The client may listen to the `Stdout` stream for logging information from the server.
 
     You may specify the port for http using the `-p <port>` flag.
-2. Stdio (using the flag `--stdio`)
+2. Stdio (using the `omnisharp` package)
   Stdio uses the standard process interfaces.  The server will read `Stdin` for requests, and pipe responses back out over `Stdout`.  Each line on either interface is a single request / response.  With this interface, the server can have a two-way relationship with the server, such that the server can intelligently provide information for the client to consume.  This can be anything from Diagnostics, to new references, package restores, and so on.
 
-        OmniSharp.exe --stdio
+    You may specify the encoding for `Stdin` and `Stdout` streams using `-e <encoding>` flag.
 
 ## Solutions
 When starting the server you must specify a solution file, or a directory where OmniSharp will find a solution.