Updates to ascii.py and README.md so that we use the same PGraph to produce planar embedding and the mapping of the PGraph nodes to their original labels.

[wbkboyer]

Resolves #72

Type of change

Please check only relevant options:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Changes

Added

• N/A

Updated

• examples/classic/ascii.py - now create a single PGraph instance from the edgelist (a $K_5$-minus-edge), for which we produce the planar rendition and which we query for the mapping() of nodes to their original labels.
• README.md - updated IDLE example to use the same technique as ascii.py. Also fixed formatting of license, since using non-breaking spaces is the cleanest way to indent paragraph contents (otherwise, you'd have to wrap each line in a <p style="indented">Contents</p>)
• .gitignore - somehow my local git started to pick up my virtual environment, so now any virtual environment prepended with . and ending in env should be ignored.

Removed

• N/A

Testing

Visually inspected that multiple runs of ascii.py show that (a, b) is not included in the resulting rendition

(.venv) planarity % python examples/classic/ascii.py
{1: 'e', 2: 'b', 3: 'd', 4: 'a', 5: 'c'}
----1----
| | |   |
| | -3--|
| |  ||||
| -2--|||
|  |  |||
---5---||
 |     ||
 ---4----

(.venv) planarity % python examples/classic/ascii.py
{1: 'd', 2: 'a', 3: 'b', 4: 'e', 5: 'c'}
----1----
| | |   |
| | -4--|
| |  ||||
| -3--|||
|  |  |||
---5---||
 |     ||
 ---2----
         

(.venv) planarity % python examples/classic/ascii.py
{1: 'c', 2: 'b', 3: 'd', 4: 'a', 5: 'e'}
----1----
| | |   |
| | -5--|
| |  ||||
| -2--|||
|  |  |||
---3---||
 |     ||
 ---4----
         

(.venv) planarity % python examples/classic/ascii.py
{1: 'c', 2: 'a', 3: 'e', 4: 'd', 5: 'b'}
----1----
| | |   |
| | -3--|
| |  ||||
| -5--|||
|  |  |||
---4---||
 |     ||
 ---2----
         

(.venv) planarity % python examples/classic/ascii.py
{1: 'b', 2: 'c', 3: 'a', 4: 'e', 5: 'd'}
----1----
|  |    |
|  --4--|
|   || ||
--5--| ||
 ||  | ||
 |--3--||
 |    |||
 ---2----
         

Details

[john-boyer-phd]

Now that #70 is in (great work), please update with latest from main and resolve merge conflicts.