- Add a README
- Move non-dynesty examples into separate sub-directory to avoid
repeatition
- Standardize variable names
- Remove the multidimensional gaussian: the 15d example is better and
more complete
- Remove the start_mcmc_chains_near.. example: this is demonstrating a
rarely used feature of a rarely used sampler, better to put this into
the docs if needed.

?

 - complete the radioactive decay example to test the Poisson
   likelihood
 - refs Monash/tupak!132

 - this example is not finished yet!

- Adds in comments from Denyz, and general tidy up.
- Closes #83

- Moves the hyperPE likelihood to core
- Adds the GaussianLikelihood
- Update docs
- Update examples

Previously I was setting the noise_log_likelihood to nan in a confusing
way. This removes that and also renames all the liklihoods for clarity.

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