Correct createHistoryName argument name (#64)

* Correct createHistoryName argument name

Previously the example and the table documenting the arguments used
conflicing names. This commit attempts to correct that and document what
is actually going on.

Related to #38. I
confirmed that Patchwork uses `seq` and not `sequence` when producing
messages however it seems that the code usually accepts both of those
arguments.

Given that `sequence` seems to be preferred we should standarise on it
in the future and document this behaviour.

* Improve wording of the side note

index.html

@@ -971,7 +971,7 @@ <h5>Implementations</h5>
                 <td>Public key of the feed to return messages from. Required.</td>
             </tr>
             <tr>
-                <td>seq</td>
+                <td>sequence</td>
                 <td>Only return messages later than this sequence number. If not specified then start from the very beginning of the feed.</td>
             </tr>
             <tr>
@@ -991,6 +991,9 @@ <h5>Implementations</h5>
                 <td>If true, also include message IDs and timestamps of when each message was received by this peer. If false, just send the messages themselves. Default: true.</td>
             </tr>
         </table>
+        <aside style="align-self: start; position: relative; top: 60px;">
+            <p>Clients must use the name <em>sequence</em> when producing requests. However for legacy reasons both <em>sequence</em> and <em>seq</em> should be accepted as the name of this argument when receiving requests. If that behaviour is supported then receiving both <em>sequence</em> and <em>seq</em> arguments with conflicting values must be considered an error.</p>
+        </aside>
 
         <p>Here is a comparison of <em>createHistoryStream</em> responses with <em>keys</em> set to true and false:</p>