Use PEP8 naming

[EarlMilktea]

Description of the change:

Rename everything violating PEP8 naming convention.

[codecov]

Codecov Report

Attention: Patch coverage is 73.73913% with 151 lines in your changes missing coverage. Please review.

Project coverage is 76.26%. Comparing base (e15dee2) to head (0bc7d28).
Report is 1 commits behind head on master.

Files	Patch %	Lines
graphix/visualization.py	3.37%	86 Missing ⚠️
graphix/gflow.py	69.72%	33 Missing ⚠️
graphix/pattern.py	88.39%	21 Missing ⚠️
graphix/transpiler.py	95.23%	6 Missing ⚠️
graphix/graphsim/basegraphstate.py	66.66%	2 Missing ⚠️
graphix/sim/tensornet.py	66.66%	2 Missing ⚠️
graphix/channels.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #199      +/-   ##
==========================================
+ Coverage   76.19%   76.26%   +0.06%     
==========================================
  Files          37       37              
  Lines        5739     5739              
==========================================
+ Hits         4373     4377       +4     
+ Misses       1366     1362       -4     

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[thierry-martinez]

Looks good to me. I just made two minor remarks.

[masa10-f]

Looks good to me!

[shinich1]

@EarlMilktea thanks! please make sure docs build without error, and add a line or two to CHENGELOG.md.

[EarlMilktea]

@shinich1 Done!

[shinich1]

@EarlMilktea please add in [unreleased] part.