Implement proper XML parsing, fix QoS parsing / acks, add disable_auth_cert

[bluemods]

This aims to enable the client to auto reconnect properly, handle connection failures, and parse stanzas using pull parsing.

Some notes:

• http package was renamed to content, this is required to fix a conflict when attempting to import the sax packages in parser.py
• the parser handles the initial k element manually, then uses a pull parser to figure out where each stanza ends. Then the result is parsed into BeautifulSoup which avoids refactoring the majority of the api which uses BeautifulSoup to navigate
• is_groupjid was changed to be more correct and return a boolean instead of throwing. A method with a `is` prefix should be returning a boolean by convention, this is a better way to write it.
• We add a new package to requirements called defusedxml, this safely parses the xml without trying to resolve entities, DTDs, etc, which XMPP / Kik does not use.
• lxml package is added to assist with xml serialize / deserialize
• We add a new constructor parameter to the Kik Client disable_auth_cert, default false. When true, auth cert is skipped. I include this option because generating auth certs is slow, and is generally not needed for most users of the API.
• It probably needs a test by others than me, as there could be a bug or some unexpected behavior changes.

[tomer8007]

Thank you for this awesome pull request.

1. If everything inside the http directory deals with HTTP requests, maybe it will be better to rename it to http_requests?
2. At which cases you could enable disable_auth_cert and can this be automated?

[bluemods]

1) I renamed http to http_requests to resolve that 2) auth certs have one purpose, this is to sign JWTs for clients using the Kik browser and wanting to authenticate their account for web requests (like linking their account to a game and proving ownership, or authenticating against a Kik web-service like the sticker and emoji inventories). This functionality is part of the kik.js library, for which the docs have been taken offline but it still works and I have a copy of them. This library doesn't currently implement the functionality to create JWTs / sign requests, so it won't have a use for most people.

I made an archive of the kik.js docs. Search for kik.sign to read more about it

[tomer8007]

Oh I see. So the auth cert request was added by @kandnub in 9ea8795063a353a212b8b8383f12c97469ddc729. Do you think we can have disable_auth_cert=True by default? Or even remove the self.authenticator.send_stanza() line?

[bluemods]

Oh I see. So the auth cert request was added by @kandnub in 9ea8795. Do you think we can have disable_auth_cert=True by default? Or even remove the self.authenticator.send_stanza() line?

True by default, sure, but I don't see a reason to remove it entirely.

[tomer8007]

I don't see a reason to remove it entirely.

We won't remove the AuthStanza class of course, but why would anyone want to create a bot with disable_auth_cert=False? Can you give one example?

[bluemods]

JWT signing / requests could be implemented for interacting with websites or unlocking all the emotes in Kik's emote shop, for example. But it is a very niche use case so I did change it to be disabled by default.