Merge branch 'updating-priors' into 'master'

docs/prior.txt

examples/injection_examples/basic_tutorial.py

...injection_examples/basic_tutorial_dist_time_phase_marg.py

...ples/injection_examples/basic_tutorial_time_phase_marg.py

examples/injection_examples/change_sampled_parameters.py

examples/injection_examples/how_to_specify_the_prior.py

examples/supernova_example/supernova_example.py

setup.py

test/prior_tests.py

tupak/core/prior.py

tupak/core/prior_files/binary_black_holes.prior

tupak/core/sampler.py

tupak/gw/likelihood.py

tupak/gw/prior.py