Fixes a few minor syntax errors and reformat the code for readability

- 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

Moritz Huebner: Added check if the prior has been set to None. Will set it to an empty dict in that case.

Adds decoding for single strings and list of strings

See merge request Monash/tupak!50

Fix one of the sub issues in #75. Namely plot_corner will now run for
data generated by python 2 when imported into python 3

An issue with html5lib upstream is causing the docs to not be generated.
This ensures a version is used that will make the docs.

Adding documentation

See merge request Monash/tupak!49

add cosmic explorer on top of H1, this has a minmum frequency of 10 Hz which is below the minimum frequency in lal_binary_black_hole, this should be fixed