Merge branch 'master' of https://github.com/nstanger/process_podcast

Added original design notes

Corrected value of dynadnorm b option ...

Should be “b=1”, not “b=y”. (closes #38)

Updated software requirements ...

• Added FFmpeg and ImageMagick.
• Tested to work with Python 3.5.

Ref #37.

Removed unnecessary VS Code workspace

Documented how to run unit tests.

Removed unnecessary main body blocks and #! lines (closes #31 for now).

Added unit tests for the FrameSegment class (ref #31).

Added missing test message (ref #31).

Rearranged tests into more appropriate locations (ref #31).

Rationalised some unnecessary code (ref #31).

Added tests for VideoSegment class (ref #31).

Extracted some Segment-specific tests (ref #31).

Added tests for the AudioSegment class (ref #31).

Added shared tests for segment classes (ref #31).

Renamed format variable more sensibly.

Corrected suffix specification for Pathlib (ref #32).

Moved progress bar tests into correct location (WTF?!) (ref #31).

Moved shared tests into package declaration (ref #31).

Added unit tests for ProgressBar class (ref #31).

Added test subpackages for progress bar and segment (ref #31).

Refactored progress bar class into subpackage.

Refactored segment classes into a subpackage.

Further refactored shell command tests into a subpackage.

Refactored shell commands and tests into a subpackage.

Added test for build_complex_filter() (ref #31).

Finished test for append_concat_filter() (ref #31).

Clarified confusing comment.

Added requirement for Python ≥ 3.7 (ref #32).

Dropped use of OrderedDicts (ref #32).