Support Yahoo Finance API Key

[TACIXAT]

Yahoo finance API is rate limited, with higher limits available if you use an API key. Would be cool to be able to plug that in when querying.

Thanks for the great library!

[ackleymi]

Thanks for using it & thanks for the feedback. I've thought of this, but I'm unsure if there is an easy way to go about it. Is there a canonical example somewhere of using a yahoo api key for finance stuff?