Improve cosmology use

See merge request !271

# Conflicts:
#   CHANGELOG.md
#   bilby/gw/__init__.py

Converts the read_in_result function to a class method

See merge request !345

Improves the load_data_from_cache_file function

See merge request !348

basic checkpointing and resuming

Closes #282

See merge request !346

Utils upgrade

Closes #153

See merge request !298

# Conflicts:
#   CHANGELOG.md

- Parameterise by the simpler start_time rather than a trigger time
- Uses the lal functions to read in the lines of the cache file
- Promote warning messages to raised errors if the data is not
  succesfully loaded
- Add doctsings

Resolve "Consistency of constants between bilby and lalsuite"

Closes #224

See merge request !343

Add slack workspace, update the summary info, and add conda forge badge

See merge request !342

Adds new docker image and 0.3.5 singularity

See merge request !344

The function remains, but just uses the class method.

Allow emcee to work with pre-release versions

See merge request !340

Allow pickling with dill to enable use of emcee 'pool' option

See merge request !341

Changed docstring: bilby.gw.waveform_generator.WaveformGenerator

See merge request !339