Expand cpppo.history to include historical file I/O, better TZ handling
o Break out timestamp related stuff into history/times.py
o Try to improve the handling to timezone abbreviations; not yet
  handling non-DST zone abbreviations.
o Bump version to 2.5
Implementation and tests of timezone abbreviation handling
o Run unit tests in a known timezone, for deterministic local results
o Add tests for timezone abbreviation regions with incompatibilties
o Add local results for non-DST 'MST' timezone
o Avoid running timestamp related unit tests if 'pytz' unavailable
Cleaned up some logging issues, fixed EtherNet/IP parser
o Do not do logging.basicConfig except when 'main' being run.
o If the cpppo.server.enip.client detects a non-zero status, report it,
  including any non-empty status_ext error code data.
o Properly parse EtherNet/IP CIP status and extended status data
Version 2.5.  Merge branch 'feature-history-files'