when we don't have enough headers, continue safely instead of aborting ( closes: https://github.com/kdeldycke/maildir-deduplicate/issues/16 )
ignore mails ONLY when we don't have enough headers; die on all other errors
work around dying on "ValueError: year out of range"
in return time.strftime('%Y/%m/%d UTC', time.gmtime(utc_timestamp))
Merge pull request #17 from mnalis/master

when not enough headers, continue safely instead of aborting