Added nasdaq provider

[lfield]

This nasdaq data provider is a replacement for quandl which is now delivered via Nasdaq Data Link.

It is essentially a copy and rename of the quandl data provider.

[JmmCz]

Please add some tests, similar like we have for other data providers

[lfield]

I can't find a test for the quandl data provider which this is based on. The challenge with test this is the API key.

[JmmCz]

We need to write new tests. Let's also not focus that much on Quandl, as this is very old data provider (a few years) and some parts of the code will require better testing and implementation. We will prepare a CR.

[lfield]

Please could you contact me directly via email so we can discuss what tests are needed.