[MRG] Image format convert merge

[tgsmith61591]

I made several changes to the package that you will probably want in your branch. Notable changes:

• The image conversion utilities are in a new sub-package called "image":

- pytolemy
  |__datasets
  |__image
    |__ format.py
  |__utils

I've kept your tests and moved them over to the "image/tests" directory, with some minor amendments. You can go from here...

• The test dataset we were using didn't have a TIFF file in it. Now it does, so the zip repo is significantly larger. Let's avoid at all costs updating this any further or our git history will grow quite large (TIFFs evidently cannot compress very well at all).

• A couple new testing utils in pytolemy.utils.testing that will make your life easier:

  • get_test_image_dir
  • get_test_image_files

The conversion code is still yours to write, just making the organization and testing a little more intuitive because sleep eludes me 🤓 ☕️

[codecov-io]

Codecov Report

Merging #6 into image_format_conversion will increase coverage by 0.45%. The diff coverage is 97.05%.

@@                     Coverage Diff                     @@
##           image_format_conversion       #6      +/-   ##
===========================================================
+ Coverage                    97.72%   98.18%   +0.45%     
===========================================================
  Files                            8       15       +7     
  Lines                           88      165      +77     
===========================================================
+ Hits                            86      162      +76     
- Misses                           2        3       +1

Impacted Files	Coverage Δ
pytolemy/utils/distance.py	100% <ø> (ø)	:arrow_up:
pytolemy/utils/__init__.py	100% <ø> (ø)	:arrow_up:
pytolemy/image/tests/test_format.py	100% <100%> (ø)
pytolemy/utils/tests/test_testing.py	100% <100%> (ø)
pytolemy/image/tests/__init__.py	100% <100%> (ø)
pytolemy/datasets/tests/test_caching.py	100% <100%> (ø)
pytolemy/image/__init__.py	100% <100%> (ø)
pytolemy/utils/testing.py	100% <100%> (ø)
pytolemy/datasets/tests/__init__.py	100% <100%> (ø)
pytolemy/image/format.py	100% <100%> (ø)
... and 10 more

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