0.4 - store zoneinfo files in PROGMEM

• 0.4 (2019-07-09, TZ DB version 2019a, beta)
  • Support the less-than-or-equal syntax {dayOfWeek}<={dayOfMonth}
    appearing in version 2019b of the TZ Database which contains Rule Zion, 2005 to 20012, IN Apr, ON Fri<=1.
  • Add BasicZoneManager and ExtendedZoneManager to retrieve ZoneInfo
    from TZ Database string identifier (e.g. "America/Los_Angeles").
  • Add configuration options (ACE_TIME_USE_BASIC_PROGMEM and
    ACE_TIME_USE_EXTENDED_PROGMEM) to place zoneinfo
    files into PROGMEM to save static RAM.

0.3.1 - add copyright notices to source files

• 0.3.1 (2019-06-30, beta)
  • Add copyright notices on source files.
  • Fix typos and formatting of README.md and USER_GUIDE.md.
  • No functional change from 0.3.

0.3 - support Link entries from TZ Database

• 0.3 (2019-06-28, beta)
  • Support Link entries from TZ Database files as C++ references to
    corresponding Zone entries.
  • Add backward and etctera files from TZ Database to the tzcompiler.py
    processing. ExtendedZoneSpecifier now supports every Zone and Link
    entry in the TZ Database (except those in backzone and systemv).
  • Add better zone and link name normalization. Convert + into _PLUS_,
    all other non-alphanumeric (0-9a-zA-Z_) converted to underscore _.
  • Move validation unit tests into separate tests/validation directory.
    Use Makefiles to generate validation_data.* files dynamically at compile
    time.

0.2 - better handling of gaps and overlaps in wall time with some date normalization

• 0.2 (2019-06-26, alpha)
  • Reduce flash memory size of WorldClock by removing extra font.
  • Split USER_GUIDE.md from README.md.
  • Rename ace_time::provider to ace_time::clock and rename
    SystemTimeProvider to SystemClock.
  • Add HelloSystemClock example code.
  • Add isValidYear() into various forComponents() methods to check
    int8_t range of year component.
  • Rename DateStrings::weekDay*() methods to dayOfWeek*() for
    consistency.
  • Change ZonedDateTime::printTo() format to match Java Time format.
  • Remove friend declarations not related to unit tests.
  • Remove redundant definitions of kInvalidEpochSeconds, standardize on
    LocalDate::kInvalidEpochSeconds.
  • Make timeOffset a required parameter for constructors and factory
    methods OffsetDateTime instead of defaulting to TimeOffset().
  • Make timeZone a required parameter in constructors and factory methods
    of ZonedDateTime.
  • Fix BasicZoneSpecifier::getOffsetDateTime() to handle gaps and overlaps
    in a reasonable way, and perform some amount of normalization.

0.1 - initial release

• 0.1 (2019-06-15)
  • Initial release on GitHub to establish a reference point.