Merge branch 'master' into improve_cosmology_use

bilby/core/sampler/__init__.py

bilby/core/sampler/base_sampler.py

bilby/core/sampler/emcee.py

bilby/core/sampler/ptemcee.py

bilby/core/sampler/pymc3.py

bilby/gw/__init__.py

bilby/gw/likelihood.py

bilby/gw/result.py

docs/basics-of-parameter-estimation.txt

examples/open_data_examples/GW150914_advanced.py

examples/open_data_examples/read_gracedb_data.py

examples/tutorials/basic_ptmcmc_tutorial.ipynb

test/gw_result_test.py