Fix svZeroDVisualization tests

[menon-karthik]

Current situation

Closes #133
The current tests for svZeroDVisualization are failing because the method used to compare generated with expected dot files is sensitive to file timestamps, spaces, etc.

Release Notes

Fixed the testing so that the generated and expected dot files are compared line-by-line.
Also fixed a couple of typos in the documentation.

Documentation

N/A

Testing

This fixes the testing.

Code of Conduct & Contributing Guidelines

• I agree to follow the Code of Conduct and Contributing Guidelines.

[emilinmathew]

The changes to tests/test_dirgraph.py look good, particularly the logic for comparing the generated and expected dot files. The use of readlines() ensures a clean comparison between the two files. Thanks for fixing the bug!