- Add doc file on CBC PE
- Add introduction text

allow aligned spin with a<0

See merge request Monash/tupak!48

Moritz Huebner: Introduced a __repr__format_helper method to help automating __repr__ formatting for all subclasses.

Makes the decoding less aggressive. This was causing various things to
be coerced into a list when they where dictionaries etc.

- Reduces the length of the output
- Explicitly states if it is a logz ratio or just logz

If lalsim is not installed just add a warning rather than raising an
error. Previously this did already exist in source.py, but we now also
import lalsim in conversion.py as well

- Renames run_sampler to run_external_sampler to differentiate it from
  the tupak run_sampler command
- Minor fixes elsewhere to code

Allows easier access to the Likelihood, GWT, WaveformGenerator, and
run_sampler

- Renames the functin to show it is the `posterior` attribute which is
  generated

- Add the label to the saved prior
- Remove obsolete write function

Fixes one issue in #75

Previously renamed example not updated in tests

min and max as properties for interpolated prior

See merge request Monash/tupak!47