PEP8 for names

[sbenthall]

Addressing #907.

Currently in this PR, only core.py has been converted over.
This is mainly a matter of automated Find and Replace and making sure tests pass.

One change: the original core.py had a variable read_shocks and a method readShocks. In order to avoid name conflict, The method is now named read_shocks_from_history.

Will look this over with others on Thursday and assuming it passes first inspection, I'll do the rest of the library.

• Tests for new functionality/models or Tests to reproduce the bug-fix in code.
• Updated documentation of features that add new functionality.
• Update CHANGELOG.md with major/minor changes.

[codecov-io]

Codecov Report

Merging #953 (5d9b836) into master (c6b3b22) will not change coverage.
The diff coverage is 85.33%.

@@           Coverage Diff           @@
##           master     #953   +/-   ##
=======================================
  Coverage   71.43%   71.43%           
=======================================
  Files          62       62           
  Lines        9145     9145           
=======================================
  Hits         6533     6533           
  Misses       2612     2612           

Impacted Files	Coverage Δ
HARK/datasets/SCF/WealthIncomeDist/SCFDistTools.py	78.04% <ø> (ø)
HARK/estimation.py	0.00% <0.00%> (ø)
HARK/ConsumptionSaving/ConsIndShockModelFast.py	51.05% <30.00%> (ø)
HARK/interpolation.py	41.06% <31.57%> (ø)
HARK/distribution.py	79.86% <76.19%> (ø)
HARK/dcegm.py	49.25% <81.81%> (ø)
HARK/ConsumptionSaving/ConsPortfolioModel.py	67.27% <85.00%> (ø)
HARK/core.py	89.59% <88.28%> (ø)
HARK/ConsumptionSaving/ConsIndShockModel.py	83.39% <89.65%> (ø)
HARK/utilities.py	32.23% <90.90%> (ø)
... and 30 more

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