Beta 4 - More Call API Support

🔨 Changed how underlying collection / resource concepts are applied:

• Moving to both collections and resources being client aware.
• Moving away from the concept of each API having a 'client' (now represented by collections / resources)

✨ Added live call support:

$call->stream->setUrl($url);
$call->stream->put();
Need to add fluent interface, and some convience methods.

✨ Can pass arbitrary data to JWT generation:

Per general spec (#22)

🔨 Update of signature generation:

Based on changes to the API: #29