inherit CSVLog from Struct
new ParameterSet, create_parameter_sets()

- new analyses/parameter_sets.py
new ParameterSet.override()
ENH: support parameter sets in fit_von_mises.py

- new --output-dir, --conf options
- --pars renamed to --parameters, order is kappa, mu, ...
- update get_start_params()
new examples/parameter_sets.py
fit_von_mises.py: new --no-neg-shift option
fit_von_mises.py: create parameter sets and logs in their respective modules

- new ParameterSets, create_logs()
fix default_conf
fit_von_mises.py: move main() body loop to new analyze()
update analyze(), fit() to obey solver options in parameter set
update default solver parameters
ENH: update CSVLog to store data in items attribute, simplify flags

- update log_results()
update printing of progress and results
new print_results()
ENH: add basic summary of fitting results

- new make_summary(), print_summary()
add 'model_class' attribute to ParameterSet

- fix _override() for defaults as dict
fix make_summary() for single parameter set
REF: rename DataSource.state -> .source_data

- DataSource.get_state() -> .get_source_data()
- update analyze()
ENH: support binned mixture estimation class in fit()

- update default_conf
move ex_fit_vonmises.py into examples/