Merge branch '207-pep8-imports' into 'master'

bilby/core/likelihood.py

bilby/core/prior.py

bilby/core/result.py

bilby/core/sampler/base_sampler.py

bilby/core/sampler/cpnest.py

bilby/core/sampler/dynesty.py

bilby/core/sampler/emcee.py

bilby/core/sampler/nestle.py

bilby/core/sampler/ptemcee.py

bilby/core/sampler/pymc3.py

bilby/core/sampler/pymultinest.py

bilby/core/utils.py

bilby/gw/conversion.py

bilby/gw/prior.py

bilby/gw/waveform_generator.py

bilby/hyper/likelihood.py

bilby/hyper/model.py