Alpaca-trade-api

In this release we:
* reconnect when the data websocket disconnects
* add type hints for the rest and stream modules
* add some input validators for URLs, price floats and dates
* remove deprecated polygon api wrappers: historic_trades, historic_quotes, splits
* add integration with pyup
* change the package requirements to be less strict
* update the README documentation

fixes:
* historic_agg_v2 now accepts different date formats
* adjust the sample code: martingale.py to work with the new data api

Alpaca Data API's new endpoints are supported as of this version.

- get_last_trade()
- get_last_quote()
- StreamConn() can now connect to streams of trade, quotes and minute bars provided by Alpaca streaming endpoint

Now all users (with or without live brokerage account) can access realtime quotes/trades both in REST and streaming.

As part of these changes, this release defaults streaming connection to the Alpaca streaming endpoint. If you want to keep using Polygon streaming endpoint, you will need to specify `data_stream` in the `StreamConn()` initializer, as

py
conn = StreamConn(data_stream="polygon")

For the compatibility with other entities around, we alias "start" to also be "timestamp" in the streaming bars.

This is another pre-release for 0.47. In this release we:
* removed the polyfeed prefix
* better exception handling for stream2
* support the new data schema:
* trade in WS: rename “sym” to “T”, “t” to be nanoseconds (from milliseconds)
* quote in WS: no change
* bars in WS: rename “sym” to “T”
* trade in REST: timestamp resolution is now nanoseconds
* quote in REST: timestamp resolution is now nanoseconds
* bars in REST: no change

This is another pre-release for the upcoming Alpaca Data API upgrade. This release notably changes the default streaming connection from polygon to alpaca. The caller can still choose polygon with `data_stream='polygon'` in StreamConn initializer.

This is the first RC release to support new Alpaca Data API.

- get_last_trade()
- get_last_quote()
- StreamConn() can now connect to streams of trade, quotes and minute bars