Remove allowing `dict` arg to `connect()` and other backward compatible

[dhalbert]

From #199 (comment):

• Include the backwards compatible API (with appropriate documentation), so that old code will work. Merge and release this any time between now and just before 9.1.0 final.
• Before releasing 9.1.0 final, update frozen libraries for 9.1.0 final with the upward compatible release. 9.1.0 will then work with the secrets dict and with the new API.
• After 9.1.0 final is released, we can change the Guide code to use the separate SSID and password arguments.
• Sometime after that, maybe 9.2 or 10.0, remove the backward compatibility.