Time zone changes not supported

[kitchoi]

When one travels to another time zone, they can get the following error when getting a report:

Traceback (most recent call last):
  File "/usr/local/bin/utt", line 11, in <module>
    sys.exit(main())
  File "/Library/Python/2.7/site-packages/utt/__main__.py", line 46, in main
    handler(args)
  File "/Library/Python/2.7/site-packages/utt/cmd_report.py", line 42, in execute
    report_date, util.entries_from_file(args.data_filename))
  File "/Library/Python/2.7/site-packages/utt/cmd_report.py", line 88, in _filter_and_group_entries
    all_entries))
  File "/Library/Python/2.7/site-packages/utt/util.py", line 40, in entries_from_file
    (i, previous_entry, new_entry))
Exception: Error line 44. Not in chronological order: 2018-08-07 19:49 break** > 2018-08-07 19:35 project

If the latter entry was logged 14 minutes later, the error would not happen and the report would be wrong, with or without the user noticing it.

I would propose logging with time zones. For backward compatibility (and for those who never cares), timestamps without time zones will be treated in local time zone. Would that be okay? I can open a pull request to fix this. My colleagues and I travel a lot as part of our job.

[larose]

Sounds good to me. Let's finish #9 first though.

[larose]

Let's put this on hold. I need to think about it.

[kitchoi]

@larose I only saw your above comment when I was ready to push (#11). It would be good to know your thoughts on this!