Add interactive LC plotter plotlc.py

[emirkmo]

This is a simple lightcurve plotting script that would be nice to have inside of flows as an optional script. However, it needs pandas and mplcursors, as well as Qt5Agg backend. It's only for us to use when diagnosing template subtractions as it allows one to quickly plot a selection of files or a target and can click on the individual points to get the fileID#. To make it easy for those doing imagematch template subtraction, I think we should bundle it with flows.

We can leave it as an optional script that requires the user to get the additional required packages to run.

[codecov-commenter]

Codecov Report

Merging #4 into devel will decrease coverage by 0.09%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##            devel       #4      +/-   ##
==========================================
- Coverage   18.43%   18.34%   -0.10%     
==========================================
  Files          15       15              
  Lines        1036     1052      +16     
==========================================
+ Hits          191      193       +2     
- Misses        845      859      +14     

Impacted Files	Coverage Δ
flows/plots.py	12.59% <0.00%> (-0.02%)	⬇️

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[rhandberg]

Could I get you to do run flake8 on that code and clean up the worst errors it throws before we include it... There are some dependencies that are not used anyway and other minor stuff. You can see an example of the output here:
https://travis-ci.org/github/rhandberg/flows/jobs/725180138

[rhandberg]

Normally I use the convention of having any command-line scripts have a name like run_<something>.py, i.e. starting with "run_". Should we keep that convention? In which case you should rename the file to something like "run_plotlc.py"

[emirkmo]

I'll fix this up and change the name too. Good call

[rhandberg]

Also, (and I know this is a source of controversy!) the rest of the code uses TABS to indent, and not spaces... You can just search-and-replace 4 spaces with 1 tab...

[emirkmo]

Ok everything but spaces/tabs is basically fixed. I have all my editors set-up to use spaces so I really don't want to delve into that right now..

[emirkmo]

Change test to check 3.8 instead of 3.5, then let's go ahead and merge this.