[OKEX] Support for API v3

[declan94]

OKEx has launched their new version of API (v3). Although API v3 and v1 are currently both supported, API v1 will be totally removed someday in the future. So the support for API v3 needs to be added into this repo.

[Flemingjp]

I recommend a similar approach to #205 - essentially deprecate the old api and produce a new api, under a new package/project for v3

[slix007]

Okex has set the deadline. See https://support.okex.com/hc/en-us/articles/360021935351

We will no longer support certain endpoints of our V1 WebSocket API, including those for order placement & cancellation, order & account enquiries (excluding subscription endpoints, please see below for details), from 5am Feb 20, 2019 (CET, UTC+1).

[badgerwithagun]

I assume you mean #261, @Flemingjp.

I guess there are no developer/users of xchange-stream that use Okex, otherwise we would have seen a PR to fix this.

If anyone needs this, a bounty may help - make it worth someone's while.

[Flemingjp]

Essentially yes, I believe a bounty is the way to go with this - as it essentially seems to be few users and fewer developers using this exchange

[mdvx]

Whats the status of this? I have 80% of OkEx working on the v3 api - happy to provide the code

[catena2w]

Is OKEX code still broken? It would be nice to remove it from README in such a case to prevent users to spend time for integration with the broken code..