Added pytest fixtures and config for Logot configuration

[etianen]

• Reduced dependency on stdlib logging module to hopefully remove all runtime dependencies when using 3rd-party logging frameworks (see Support loguru log capture #28)
  • No longer using logging.getLoggerName() to format log levels.
  • No longer supporting logging.Logger type in default Logot class attrs.
• Added pytest fixtures and config for Logot configuration
• Tested using pytester fixture.
• Updated docs.