Some housekeeping items

[mwcraig]

This PR has a fews bits in it:

• Add regression test for Fix bug when ImageFileCollection.filter() would return an empty collection #750
• Add new section to AUTHORS.rst and update list

[mwcraig]

@crawfordsm -- are you ok with the new added section to AUTHORS.rst? I'd like to acknowledge these folks in some way. Currently thinking opening more than one issue or something equivalent gets one added here.

@MSeifert04 -- I moved you to a new section of AUTHORS.rst. Does this look to you?

[codecov]

Codecov Report

Merging #764 (5a81092) into master (46ccaed) will increase coverage by 0.13%.
The diff coverage is 92.30%.

@@            Coverage Diff             @@
##           master     #764      +/-   ##
==========================================
+ Coverage   95.36%   95.49%   +0.13%     
==========================================
  Files          30       30              
  Lines        3906     3931      +25     
==========================================
+ Hits         3725     3754      +29     
+ Misses        181      177       -4     

Impacted Files	Coverage Δ
ccdproc/combiner.py	93.11% <50.00%> (+0.08%)	⬆️
ccdproc/tests/test_combiner.py	100.00% <100.00%> (ø)
ccdproc/tests/test_image_collection.py	98.87% <100.00%> (+<0.01%)	⬆️
ccdproc/core.py	97.24% <0.00%> (+0.21%)	⬆️
ccdproc/image_collection.py	99.19% <0.00%> (+0.26%)	⬆️
ccdproc/utils/sample_directory.py	100.00% <0.00%> (+6.89%)	⬆️

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[MSeifert04]

That's fine by me. Thank you!