During setup, this writes a file tupak/.version which contains the git
hash and change date. We can extend this in future to contain other
information. This is then printed when the logging is initialised.

Revert "Revert "Moritz Huebner: Removed default parameters for sampling frequency and time duration in the waveform generator""

This reverts commit 91e90f0d.

Revert "Moritz Huebner: Removed default parameters for sampling frequency and time duration in the waveform generator"

This reverts commit e4ac1430.

Moritz Huebner: Removed default parameters for sampling frequency and time duration in the waveform generator

Clean up the logic of fill_priors and close #58

Closes #58

See merge request Monash/tupak!36

If a label is given to setup_logger, the output is written to a file.

- Removes the 'bad_keys' part of the logic. I believe this was
  essentially adding the keys which where not given in the prior and
  that had no default prior, and then removing them at the end.
- Change the logging output slightly: now the only warning that is given
  is when no default prior is known. Other output at info level
- Add in what the waveform_generator knows about missing keys (useful
  for diagnosis
- Formatting of the docstring

Prior tests

See merge request Monash/tupak!35

Default prior bounds

See merge request Monash/tupak!34

Allow multiple prior draws

See merge request Monash/tupak!33

- Rename n_samples to size to fit with standard numpy conventions
- Fix check to handle multiple values

Functionally, this changes nothing, but it makes it clear that the
filled priors are the dictionary `priors`.

Previously, the dynesty kwarg for the number of live points was set to
be `npoints`, and so `npoints=10000` was passed to
`dynesty.NestedSampler`. This, however, is not the kwarg requried by
`NestedSampler`, but it instead should be `nlive`.  Unfortunately, this
error is silenced because the kwargs are just lost in dynesty.

- Fixes nlive kwarg
- Reduces default number from 10000 to 250 (as this was what was
  actually used before)
- Adds a verbose flag controlling the `run_nested` argument
  `print_progress`

Add minimal example and associated helper functions

See merge request Monash/tupak!32

- Adds an example showing the simplest number of steps to run PE on
  GW150914
- Adds a helper (rapper) function to quickly get the BBH likelihood
  instance