Simplify wg redundant code

See merge request Monash/tupak!124

Add Poisson likelihood to core likelihood functions

See merge request Monash/tupak!132

Updated the eccentric inspiral example

See merge request Monash/tupak!137

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

 - change from using numpy bincount to check for non-negative
   values, as large values can cause a memory error
 - make sure log likelihood returns -inf if any rate values
   are zero
 - refs Monash/tupak!132

 - this example is not finished yet!

 - allow likelihood to use a rate function with a
   dependent variable
 - refs Monash/tupak!132

 - refs Monash/tupak!132

Adds capability to run PE on eccentric waveforms

See merge request Monash/tupak!133

Add calibration

See merge request Monash/tupak!113

# Conflicts:
#   examples/open_data_examples/GW150914.py

Merge branch '154-sample_subset-in-priorset-should-not-have-have-list-as-a-default-argument-for-keys' into 'master'

Resolve "`sample_subset` in `PriorSet` should not have have `list()` as a default argument for `keys`"

Closes #154

See merge request Monash/tupak!129

Resolve "`sample_subset` in `PriorSet` should not have have `list()` as a default argument for `keys`"

Update GW150914.py to use tupak.gw.WaveformGenerator

See merge request Monash/tupak!127

Rework ci

See merge request Monash/tupak!125