Improve shape family tests

[janbridley]

Description

More tests were added and current tests were expanded for test_shape_families.py

Motivation and Context

Plane shape families can result in unexpected errors with parameter values close to transition points in shape space. More tests were added to cover this possibility, and integer values were replaced with "exact" floats to verify that transition point shapes can be generated. These tests confirm that the unexpected failures are a result of floating point precision, and not a deeper bug in the implementation. Also note that before #188 these functions return incorrect results rather than raising an error.

Types of Changes

• Documentation update
• Bug fix
• New feature
• Breaking change¹

¹The change breaks (or has the potential to break) existing functionality.

Checklist:

• I am familiar with the Contributing Guidelines.
• I agree with the terms of the Contributor Agreement.
• The changes introduced by this pull request are covered by existing or newly introduced tests.
• I have updated the changelog and the credits.

[DomFijan]

Are 1000 max examples really needed for intermediates? it feels like this can be significantly reduced?

[janbridley]

Are 1000 max examples really needed for intermediates? it feels like this can be significantly reduced?

Hypothesis does sample better with 1000 examples, but the behavior is confirmed with the default 200 samples. I will adjust that down!