Fixes for tests and coverage

[wtgee]

• Files are linted against 3.7
• Currently ignores all config server testing because of changes w/ pytest and flask on github.
• Fix some astropy deprecation warnings for coordinate transforms.
• Fix for matplotlib axes change.
• Serial device reader thread doesn't use logging, which simplifies a lot of things and was only being used in one place.

[codecov[bot]]

Codecov Report

Merging #295 (ed94cf8) into develop (1c06552) will decrease coverage by 0.15%. The diff coverage is 72.97%.

@@             Coverage Diff             @@
##           develop     #295      +/-   ##
===========================================
- Coverage    75.25%   75.10%   -0.16%     
===========================================
  Files           27       25       -2     
  Lines         1750     1643     -107     
===========================================
- Hits          1317     1234      -83     
+ Misses         433      409      -24     

Impacted Files	Coverage Δ
src/panoptes/utils/config/server.py	39.69% <65.51%> (+2.39%)	:arrow_up:
src/panoptes/utils/images/__init__.py	67.85% <100.00%> (+0.38%)	:arrow_up:
src/panoptes/utils/images/bayer.py	100.00% <100.00%> (ø)
src/panoptes/utils/serial/device.py	100.00% <100.00%> (ø)
src/panoptes/utils/utils.py	100.00% <100.00%> (ø)
src/panoptes/utils/config/helpers.py	70.49% <0.00%> (-29.51%)	:arrow_down:
src/panoptes/utils/config/cli.py
src/panoptes/utils/config/client.py
src/panoptes/utils/rs232.py	88.79% <0.00%> (+0.29%)	:arrow_up:
... and 4 more

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