Cryptofeed

* Feature: Rest Endpoints for Historical Deribit data
* Feature: Specify numeric datatype for InfluxDB
* Bugfix: Greatly improve performance of book writes for InfluxDB
* Feature: Bybit exchange support
* Bugfix: Deribit now returning floats in decimal.Decimal
* Feature: Elastic Search backend

* Bugfix: Book Delta Conversion issue in backends
* Bugfix: Tweak BitMEX rest API to handle more errors more gracefully
* Feature: Deribit Exchange support
* Feature: Instrument channel
* Bugfix: support Kraken websocket API changes
* Bugfix: correct USDT symbol mappings for Bitfinex
* Bugfix: Fixed mongo book backend
* Feature: Book delta support for mongo, sockets, ZMQ

* Feature: Book delta support for InfluxDB
* Feature: Swaps on OkEX

* Bugfix: Fix tagging issue in InfluxDB
* Bugfix: Fix book updates in InfluxDB
* Feature: Book delta support in Redis backends
* Feature: Book delta support in Kafka backend

* Feature: Cleanup callback code
* Feature: Poloniex subscription now behaves like other exchanges
* Feature: Kafka Backend

* Bugfix: Timestamp normalization for backends were losing subsecond fidelity
* Feature: All exchanges report timestamps in floating point unix time
* Bugfix: Implement change in OkEx's trading pair endpoint for pair generation