add scipy weight tests

[raybellwaves]

Closes #254

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Performance (if you touched existing code run asv to detect performance changes)
• refactoring

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. This could point to a cell in the updated notebooks. Or a snippet of code with accompanying figures here.

Checklist (while developing)

• I have added docstrings to all new functions.
• I have commented my code, particularly in hard-to-understand areas
• Tests added for pytest, if necessary.

Pre-Merge Checklist (final steps)

• I have rebased onto master or develop (wherever I am merging) and dealt with any conflicts.
• I have squashed commits to a reasonable amount, and force-pushed the squashed commits.

[raybellwaves]

pearsonr is the only one which really needs a test, the others are covered in the non weighted version.