add 'only_colors' option to KNearNeigh #20

[sschmidt23]

Addresses issue #20 by adding an only_colors config param to KNearnNeigh, if set to True this does not use the reference band magnitude in the nearest neighbor calculation. I also added an explicit np.float32 cast to the nondetect replacements, as I noticed a ton of deprecation warnings from pandas when running the tests where it was not realizing that 27.79 was a float32 and threatening to throw an exception on a future pandas version. Also, some minor linting fixes for whitespace and such in the test_algos.py

Code Quality

• [x] My code follows the code style of this project
• [x] I have written unit tests or justified all instances of #pragma: no cover; in the case of a bugfix, a new test that breaks as a result of the bug has been added
• [x] My code contains relevant comments and necessary documentation for future maintainers; the change is reflected in applicable demos/tutorials (with output cleared!) and added/updated docstrings use the NumPy docstring format
• [ ] Any breaking changes, described above, are accompanied by backwards compatibility and deprecation warnings

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 95.81%. Comparing base (7b08951) to head (d8dc15d). Report is 2 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #21 +/- ## ========================================== + Coverage 95.80% 95.81% +0.01% ========================================== Files 4 4 Lines 286 287 +1 ========================================== + Hits 274 275 +1 Misses 12 12 ```

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