Clarify OPTIONS requests wrt Tus-Rusumabl and Tus-Version headers (#153)

From https://tus.io/protocols/resumable-upload.html#options
> A successful response indicated by the `204 No Content` or `200 OK` status MUST contain the `Tus-Version` header. It MAY include the `Tus-Extension` and `Tus-Max-Size` headers.
>
> The Client SHOULD NOT include the `Tus-Resumable` header in the request and the Server MUST ignore the header.

From https://tus.io/protocols/resumable-upload.html#tus-resumable
> The `Tus-Resumable` header MUST be included in every request and response except for `OPTIONS` requests. The value MUST be the version of the protocol used by the Client or the Server.
>
> If the version specified by the Client is not supported by the Server, it MUST respond with the `412 Precondition Failed` status and MUST include the `Tus-Version` header into the response. In addition, the Server MUST NOT process the request.

So we should omit the `Tus-Resumable` header from the OPTIONS request and clarify the example

Author: butonic

protocol.md

@@ -252,7 +252,7 @@ Server MUST ignore the header.
 ##### Example
 
 This example clarifies the response for an `OPTIONS` request. The version used
-in both, request and response, is `1.0.0` while the Server is also capable of
+in the response is `1.0.0` while the Server is also capable of
 handling `0.2.2` and `0.2.1`. Uploads with a total size of up to 1GB are
 allowed and the extensions for [Creation](#creation) and
 [Expiration](#expiration) are enabled.
@@ -527,7 +527,6 @@ checksum algorithm and the Base64 encoded checksum separated by a space.
 ```
 OPTIONS /files HTTP/1.1
 Host: tus.example.org
-Tus-Resumable: 1.0.0
 ```
 
 **Response**: