Initial WebSocket implementation.

[mucinoab]

TODO

• async
• proper error handling
• improve documentation
• better names
• more tests

[nph4rd]

@mucinoab - this is looking great! Thanks so much for this! 🎆

I've had the chance to look through most of the code included so far and I think most of my observations are covered by the checklist in the description. I noticed there are lots of unwraps atm. I should think "proper error handling" will allow us to get rid of them. Apart from that I would add the following:

• I would suggest to move some of the structs in websocket.rs into model/. This would be consistent with the rest of the code in terms of modularity. Also, the deserialize_books function could be in util.rs.

• Noticed there is an example in the docs for the BitsoWebSocket struct. I think it might be worth adding something like this to examples/ - again, in order to be consistent with the rest of the project.

All in all, I think it's looking brilliant! Let me know if there is something I can do to keep moving this forward 😄 👍