0.6.7: Fix pip installation problem and improve features & performance

• BUGFIX

  • fix pip installation problem due to incorrectly formatted
    version specifiers
  • update video duration extraction to correctly
    extract the duration of each video and avoid
    writing 'N/A'

• FEATURE IMPROVEMENTS

  • improve identification of seen videos in csv files by
    • avoiding potentially brittle regular expression matching
    • parsing each row of the csv file and extracting the
      (Video ID|Video URL) value from the corresponding column directly
  • normalize whitespace to avoid including newlines,
    carriage returns, and multiple consecutive whitespace characters
    in the video title
  • improve logging messages by including time.time() and
    time.perf_counter() when logging the time taken to perform
    an operation

• PERFORMANCE IMPROVEMENTS

  • increase write efficiency by completely avoiding writing to a
    temporary file when no new videos found for an existing file

• INTERNAL IMPROVEMENT

  • the following change does not affect the functionality of the program
    • add unit tests for the video title whitespace normalization