Replace "on/off" with "True/False" for boolean values

[douglatornell]

Original report by Doug Latornell (Bitbucket: douglatornell, GitHub: douglatornell).

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Starting with maplotlib==2.2:

Passing one of 'on', 'true', 'off', 'false' as a boolean is deprecated; 
use an actual boolean (True/False) instead.

Affected figure module(s):

• research/velocity_section_and_surface.py

[douglatornell]

Original changes by Doug Latornell (Bitbucket: douglatornell, GitHub: douglatornell).

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changed state from "new" to "open"

[douglatornell]

Original comment by Doug Latornell (Bitbucket: douglatornell, GitHub: douglatornell).

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Replace "on/off" with "True/False" for boolean values.

re: issue #66

[douglatornell]

Original changes by Doug Latornell (Bitbucket: douglatornell, GitHub: douglatornell).

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changed content from "Starting with maplotlib==2.2:

Passing one of 'on', 'true', 'off', 'false' as a boolean is deprecated; 
use an actual boolean (True/False) instead.

Affected figure module(s):

• research.velocity_section_and_surface.py" to "Starting with maplotlib==2.2:

  Passing one of 'on', 'true', 'off', 'false' as a boolean is deprecated;
  use an actual boolean (True/False) instead.

Affected figure module(s):

• research/velocity_section_and_surface.py"