Quandl

* Provide a more actionable warning when asking for data over 1M rows

* Add test support for python 3.6.

* Raise error when over 1000000 rows when fetching tables with paginate

* Pandas fix for newer pandas version.

* Bug fixes

* Bug: support column with a name 'code'

* Handle unexpected errors

* Datatables for developers
* Datatables for analysts
* Backwards compatibility
* Documentation updates