Merge branch 'updating-priors' into 'master'

examples/injection_examples/basic_tutorial.py

examples/injection_examples/change_sampled_parameters.py

examples/injection_examples/how_to_specify_the_prior.py

examples/injection_examples/marginalized_likelihood.py

examples/open_data_examples/GW150914.py

examples/open_data_examples/GW150914_minimal.py

setup.py

test/prior_tests.py

test/sampler_tests.py

tupak/core/prior.py

tupak/core/sampler.py

tupak/gw/likelihood.py

tupak/gw/prior.py

tupak/gw/prior_files/GW150914.prior

tupak/gw/prior_files/binary_black_holes.prior

tupak/gw/prior_files/comoving.txt