Some cleanup items

[timkpaine]

• Migrate to kwargs for python
• remove pickle from example
• start moving some stuff into core
• update readme, setup.py, some other bits
• update yarn clean
• remove private API tests

[codecov-io]

Codecov Report

Merging #744 into master will increase coverage by 0.49%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #744      +/-   ##
==========================================
+ Coverage   91.32%   91.82%   +0.49%     
==========================================
  Files          63       49      -14     
  Lines        3169     3093      -76     
==========================================
- Hits         2894     2840      -54     
+ Misses        275      253      -22

Impacted Files	Coverage Δ
perspective/table/view.py	80.9% <0%> (-0.18%)	⬇️
perspective/table/_data_formatter.py	95.18% <0%> (-0.06%)	⬇️
perspective/table/table.py	94.89% <0%> (-0.06%)	⬇️
perspective/core/exception.py	100% <0%> (ø)	⬆️
perspective/core/__init__.py	100% <0%> (ø)	⬆️
perspective/tests/table/test_view.py	98.55% <0%> (ø)	⬆️
perspective/tests/table/binding/test_t_gnode.py
perspective/tests/table/binding/test_make_view.py
perspective/tests/table/binding/test_t_schema.py
perspective/tests/table/binding/test_t_ctx.py
... and 13 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update de59d3e...ec92b59. Read the comment docs.

[texodus]

Looks good, thanks for the PR!