Distfit

* quantile added as new method
* percentile added as new method

* typo fix in naming
* some fixes in examples.py
* scipy library add to setup
* docstring updates

* predict returns a dict
* fit_transforms returns a dict

* save and loading
* sphinx updates
* docstring updates
* smoothing

Fast update after previous version where the following is done:

* input parameters changed: distribution into distr.
* various smaller changes

disfit is becoming more easy as the whole code is rewritten in classes now!

* distfit code refactored with classes
* examples updated
* unit test updated
* docstrings updated