Wq.io

**wq.io 0.7.0** brings a few API improvements and minor new features.

New Classes
- **[ZipFileLoader](http://wq.io/docs/loaders)** & **[ZipNetLoader](http://wq.io/docs/loaders)**: Automatically extract data from a file stored in a compressed archive.

API improvements
- **[GIS submodule](http://wq.io/docs/gis-io)**: Support for `as_dataframe()` (returns a `GeoDataFrame` with some help from [GeoPandas](http://geopandas.org/)).
- **[XmlParser](http://wq.io/docs/parsers)**: Search for `root_tag` (if specified) when parsing XML documents
- New `scan_fields` option to ensure fields are properly detected for datasets with different fields in each row

API Improvements
- Add a `as_dataframe()` function to `BaseIO` (7)
- Always use `StringIO.StringIO` in Python 2.7

- Fix minor issue with exception strings.

API Improvements
- Python 3 support (2)
- Use [requests](http://python-requests.org) for `NetLoader` (3)
- Read and write support in all *FileIO classes (`CsvFileIO`, `JsonFileIO`, `XmlFileIO`, and `ExcelFileIO`)
- Comprehensive test suite
- More robust `pickle` support
- Complete docs on [extending wq.io](http://wq.io/docs/custom-io)

API Improvements
- Add `Exception` subclasses to report common error cases (e.g. `LoadFailed`, `ParseFailed`, `NoData`) - see heigeo/climata-viewer5
- Make `TupleMapper` instances pickleable - see heigeo/climata-viewer8

API Improvements
- Formalize notion of a `nested` IO, or an IO where each record contains a pointer to another IO. This concept is used extensively by the [climata](https://github.com/heigeo/climata) library, for example in [climata.acis.StationDataIO](https://github.com/heigeo/climata/blob/master/climata/acis/__init__.pyL120).
- Added a utility function, `flattened()`, that converts nested IOs into single-level IOs through denormalization
- Other minor improvements