Move widget display to Out[...]

[westernguy2]

Overview

The widget display used to be displayed before Out[...], which is not in accordance to what Pandas usually does. This PR moves the widget to Out[...] in IPython notebooks. This PR addresses both #56 and #60

Changes

I replaced _repr_html_ with _ipython_display_ in both frame.py and vis.py. I then removed __repr__ from frame.py so that it uses the Pandas default __repr__ when the widget isn't displayed. I added a test to ensure this is the case.

Example Output

Below is an example of the widget showing up in Out[...]. Notice that Out[...] doesn't show up below the widget, which means the widget is actually in Out[...]

[codecov]

Codecov Report

Merging #308 (da6455a) into master (2553125) will decrease coverage by 0.84%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #308      +/-   ##
==========================================
- Coverage   80.87%   80.02%   -0.85%     
==========================================
  Files          50       50              
  Lines        3618     3615       -3     
==========================================
- Hits         2926     2893      -33     
- Misses        692      722      +30     

Impacted Files	Coverage Δ
lux/core/frame.py	70.25% <100.00%> (+0.08%)	⬆️
lux/core/series.py	53.84% <100.00%> (-33.78%)	⬇️
lux/vis/Vis.py	74.85% <100.00%> (ø)
lux/vis/VisList.py	51.33% <100.00%> (ø)
lux/vislib/matplotlib/ScatterChart.py	76.47% <0.00%> (+1.17%)	⬆️
lux/vislib/matplotlib/Heatmap.py	98.33% <0.00%> (+1.66%)	⬆️
lux/vislib/altair/ScatterChart.py	96.96% <0.00%> (+3.03%)	⬆️
lux/vislib/altair/Heatmap.py	96.55% <0.00%> (+3.44%)	⬆️

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[dorisjlee]

Hi @westernguy2, The improved output looks much more Pandas-consistent than what we had before! Could we use the
_ipython_display_ approach also for series.py? That way the print(series) behavior would be closer to what print(df) does.

@cjachekang, @westernguy2: Were you able to test this on Jupyter Lab? I tried this on lab but the widget doesn't seem to be displaying. It is possible that there is something wrong with my lab setup.

[dorisjlee]

This looks great, thanks @westernguy2!