Use Finnhub stock api as the new data source

Hi guys,

Big fan of Go and great project here. Just wondering if you guys are open to add https://finnhub.io/ as the new data source. Beside real-time market price (websocket supported), they also support a lot of other fundamental and alternative data for FREE.

I think this would benefit the community tremendously. With a free account, you can make 60 API requests/minute. Their documentation can be found here: https://finnhub.io/docs/api