Improve test coverage and minor bug fixes

[abhisrkckl]

See #457

[codecov]

Codecov Report

Base: 62.70% // Head: 63.24% // Increases project coverage by +0.53% 🎉

Coverage data is based on head (e7b867e) compared to base (e9c41b6).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1444      +/-   ##
==========================================
+ Coverage   62.70%   63.24%   +0.53%     
==========================================
  Files          90       90              
  Lines       20485    20487       +2     
  Branches     3534     3535       +1     
==========================================
+ Hits        12846    12957     +111     
+ Misses       6840     6745      -95     
+ Partials      799      785      -14     

Impacted Files	Coverage Δ
src/pint/derived_quantities.py	100.00% <100.00%> (+9.30%)	⬆️
src/pint/toa.py	87.28% <100.00%> (+3.42%)	⬆️
src/pint/residuals.py	67.48% <0.00%> (+0.81%)	⬆️
src/pint/orbital/kepler.py	98.19% <0.00%> (+4.07%)	⬆️
src/pint/phase.py	97.95% <0.00%> (+4.08%)	⬆️
src/pint/config.py	100.00% <0.00%> (+11.11%)	⬆️
src/pint/scripts/convert_parfile.py	83.33% <0.00%> (+83.33%)	⬆️
src/pint/scripts/compare_parfiles.py	100.00% <0.00%> (+100.00%)	⬆️

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[abhisrkckl]

I am done with this PR. There is a lot of room for improvement in this, but those can be part of future PRs.

[abhisrkckl]

Added tests from un-merged PR #1446

[dlakaplan]

This looks good. Ready to merge?

[abhisrkckl]

Yes