Pyabc

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* Reorganize distance module (minor API change:
distance_functions -> distance, and some classes shortened accordingly)
* Allow to pass parameters to Acceptor and Distance.
* Make time and parameter arguments to distance functions optional.
* Rewrite lazy evaluation for calibration sample in ABCSMC class.
* Give default values for ABCSMC.run arguments, which set no stopping
criterion.
* Add function and plot for effective sample size.

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* Run some notebooks as part of the tests.
* Automatize pypi upload via travis.

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* Save number of samples taken in calibration step in database.
* Fix error with reported number of simulations in EpsMixin based samplers.
* Fix several warnings.

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* Monitor code quality using codacy and codecov.
* Extend visualization routines: Add histogram, sample number, epsilon
trajectory, model probability, and credible interval plots.
* Test visualization routines on travis.
* Fix problem with the History.get_weighted_distances function after update to
sqlalchemy>=1.3.0.
* Add random walk based transition for discrete parameters.

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* Tidy up returning of rejected samples in Sample (not only summary
statistics).
* Recreate a population from file in History.get_population().
* Speed up loading from database by eager loading.
* Document the change of the contribution scheme to master+develop.

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* Allow for the database to save no summary statistics for testing purposes.
* Tidy up some pyabc.History methods.
* pyabc.History.id set by default to the largest index (previously 0),
corresponding to the latest inserted analysis.