Ndd

Added
- `ndd.from_data`
- `ndd.mutual_information`
- `ndd.conditional_information`
- `ndd.interaction_information`
- `ndd.coinformation`

Changed
- Python3 only
- fixed NumericError for valid entropy estimation

Added
- `jensen_shannnon_divergence()` function.
- `estimators` module.
- Entropy, KLDivergence and JSDivergence estimators.
Changed
- entropy() signature is now:
`entropy(pk, k=None, alpha=None, plugin=False, return_std=False)`

Added
- Entropy class.
- from_data() returns an estimate from a data samples

Changed
- histogram(): remove unique elements of array as optional output
- histogram(): takes the `axis` and `r` optional args

Changed
- entropy(): removed the (broken) function for estimator selection

Changed
- entropy(): renamed argument 'dist' to 'plugin'