Build fails due to whatsappweb-rs incompatibility

[fancypantalons]

The pre-futures branch no longer exists in the whatsappweb-rs project and so the build currently fails. No idea what it'll take to update the code to work with the latest version of the library (I'm a total Rust neophyte), but it prevents building a version of sms-irc that sends the latest version number of Whatsapp.

I was able to get a working sms-irc build by pulling down whatsappweb-rs, reverting 63b1acf62, and then updating the sms-irc Cargo.toml to point to my local modified source tree. But obviously that's not for the faint of heart!