New importers for Yahoo, IEX and Quandl are live

[Martin Blais]

Dear Beancounterers,

I've been busy attending to user tickets lately.

https://bitbucket.org/blais/beancount/src/4a3995617e7df5ffa3377711382c7ad2f9d8935b/CHANGES?at=default&fileviewer=file-view-default

In the process I fixed the importer situation:

- I rewrote the Yahoo price source to the v7/v8 APIs, it should work again.

- I wrote a brand new importer from IEX, which has a really nice free API.

- Hugo Ideler pointed out the existence of Quandl (thank you!), and I wrote an importer for its simple REST API (not all content is free, but a good amount of it is).

I hope this is useful to some of you. 

Let me know if you encounter any problems.

Cheers,