Datasmoothie

This release implements weighting in the datasource and fixes a bug where adding charts to a report was broken.

Increase support for datasources. Now the survey meta data is pulled automatically when a datasource is retrieved and users can get a list of the datasources variables.

Add support for
- generating tables
- weighting a datasource
- exporting to Excel

Implement retrieval of survey meta and data with the Datasource class. The result is also stored in the instance once it is fetched.

This release implements the main actions for the [report](https://www.datasmoothie.com/static/api2/index.htmltag/report) and [reportElement](https://www.datasmoothie.com/static/api2/index.htmltag/reportElement) endpoints. Both are represented by the `report` object, where the report endpoint is referred to as `report.meta` and the reportElements endpoint is referred to as `report.elements`.

This release also implements `report.add_chart()`, which is still at an experimental phase and is not very robust.

Intial release of the Python Datasmoothie API wrapper. This release only implements the interface to the datasource part of the API, specifically, getting info and updating meta-data and data.