Bandicoot

This is a small update. It includes:
- immutable dictionary order when outputting statistics,
- recharges can be loaded with date or datetimes objects,
- fixed a bug with a null denominator when computing the average balance of recharges
- fixed a compatibility bug with Python 3.7 when iterating over an empty iterator
- fixed a bug within the position binning routine (the month key was missing)
- up-to-date links to the Github repository.

Major new features
- New interactive visualization in `bc.visualization`.
- Support for mobile phone recharges (top-up).
- Ready for Python 3 (72420a5).
- Support both antenna and GPS locations with optional DBSCAN clustering algorithm.

Other updates
- Increased documentation and updated notebook.
- Faster computations (dbb9739) and smaller memory footprint (52b931f).
- Increased Python Style Guide compliance in the source code.
- Minor breaking changes for indicators (eg. 9326cb1).

We are pleased to announce the new version of bandicoot, the python toolbox to analyze mobile phone metadata. bandicoot 0.4 now includes new features and reporting variables, and supports ego-network analysis (e.g. clustering coefficient).