Add hyper-parameter likelihood

See merge request Monash/tupak!41

Move to corner

See merge request Monash/tupak!46

Fix marginalised likelihood

See merge request Monash/tupak!45

Add a new test which runs through the examples

See merge request Monash/tupak!44

 Removes chainconsumer and following requirements. These where causing
the CI to be very slow. Instead, rather than plotting, just list a
warning.

- Adds a tests flag for which the sampler only runs 100 steps
- Set the samples as random samples to test plotting
- Fix problems in a few of the examples

Not sure how this got undone, but this just repeats the same step of
setting the fixed_parameter properly

Minor change to how non standard parameters are checked

See merge request Monash/tupak!43