Updated TZ database and refactored extension trait to remove duplicat… #4

cargo test (windows-2019)

There are 0 failures, 0 warnings, and 0 notice.

Type	Count
error: internal compiler error	0
error	0
warning	0
failure-note	0
note	0
help	0

Name	Status
binary_search::tests::test_binary_search	ok
posix_tz::parser::tests::basic	ok
tests::dst	ok
tests::errors	ok
system::tests::get_timezone	ok
tests::handles_after_changeover	ok
tests::handles_backward_changeover	ok
tests::handles_broken_time	ok
tests::handles_forward_changeover	ok
tests::handles_replace_time_in_timezone	ok
tests::handles_replace_time_in_timezone_from_primitive	ok
tests::london_to_berlin_name	ok
tests::london_to_berlin	ok
tests::names	ok
tests::offsets_and_name	ok
tests::zoned_date_time_add_duration	ok
tests::find	ok