Add exact date/time support and improvements

[yunussandikci]

Hi 👋
This PR adds specifying an exact date/time in addition to duraton support to mayfly .
Example dates it supports:

        "May 8, 2009 5:57:51 PM",
	"oct 7, 1970",
	"oct 7, '70",
	"oct. 7, 1970",
	"oct. 7, 70",
	"Mon Jan  2 15:04:05 2006",
	"Mon Jan  2 15:04:05 MST 2006",
	"Mon Jan 02 15:04:05 -0700 2006",
	"Monday, 02-Jan-06 15:04:05 MST",
	"Mon, 02 Jan 2006 15:04:05 MST",
	"Tue, 11 Jul 2017 16:28:13 +0200 (CEST)",
	"Mon, 02 Jan 2006 15:04:05 -0700",
	"Mon 30 Sep 2018 09:09:09 PM UTC",
	"Mon Aug 10 15:44:11 UTC+0100 2015",
	"Thu, 4 Jan 2018 17:53:36 +0000",
	"Fri Jul 03 2015 18:04:07 GMT+0100 (GMT Daylight Time)",
	"Sun, 3 Jan 2021 00:12:23 +0800 (GMT+08:00)",
	"September 17, 2012 10:09am",
	"September 17, 2012 at 10:09am PST-08",
	"September 17, 2012, 10:10:09",
	"October 7, 1970",
	"October 7th, 1970",
	"12 Feb 2006, 19:17",
	"12 Feb 2006 19:17",
	"14 May 2019 19:11:40.164",
	"7 oct 70",
	"7 oct 1970",
	"03 February 2013",
	"1 July 2013",
	"2013-Feb-03",
	// dd/Mon/yyy  alpha Months
	"06/Jan/2008:15:04:05 -0700",
	"06/Jan/2008 15:04:05 -0700",
	//   mm/dd/yy
	"3/31/2014",
	"03/31/2014",
	"08/21/71",
	"8/1/71",
	"4/8/2014 22:05",
	"04/08/2014 22:05",
	"4/8/14 22:05",
	"04/2/2014 03:00:51",
	"8/8/1965 12:00:00 AM",
	"8/8/1965 01:00:01 PM",
	"8/8/1965 01:00 PM",
	"8/8/1965 1:00 PM",
	"8/8/1965 12:00 AM",
	"4/02/2014 03:00:51",
	"03/19/2012 10:11:59",
	"03/19/2012 10:11:59.3186369",
	// yyyy/mm/dd
	"2014/3/31",
	"2014/03/31",
	"2014/4/8 22:05",
	"2014/04/08 22:05",
	"2014/04/2 03:00:51",
	"2014/4/02 03:00:51",
	"2012/03/19 10:11:59",
	"2012/03/19 10:11:59.3186369",
	// yyyy:mm:dd
	"2014:3:31",
	"2014:03:31",
	"2014:4:8 22:05",
	"2014:04:08 22:05",
	"2014:04:2 03:00:51",
	"2014:4:02 03:00:51",
	"2012:03:19 10:11:59",
	"2012:03:19 10:11:59.3186369",
	// Chinese
	"2014年04月08日",
	//   yyyy-mm-ddThh
	"2006-01-02T15:04:05+0000",
	"2009-08-12T22:15:09-07:00",
	"2009-08-12T22:15:09",
	"2009-08-12T22:15:09.988",
	"2009-08-12T22:15:09Z",
	"2017-07-19T03:21:51:897+0100",
	"2019-05-29T08:41-04", // no seconds, 2 digit TZ offset
	//   yyyy-mm-dd hh:mm:ss
	"2014-04-26 17:24:37.3186369",
	"2012-08-03 18:31:59.257000000",
	"2014-04-26 17:24:37.123",
	"2013-04-01 22:43",
	"2013-04-01 22:43:22",
	"2014-12-16 06:20:00 UTC",
	"2014-12-16 06:20:00 GMT",
	"2014-04-26 05:24:37 PM",
	"2014-04-26 13:13:43 +0800",
	"2014-04-26 13:13:43 +0800 +08",
	"2014-04-26 13:13:44 +09:00",
	"2012-08-03 18:31:59.257000000 +0000 UTC",
	"2015-09-30 18:48:56.35272715 +0000 UTC",
	"2015-02-18 00:12:00 +0000 GMT",
	"2015-02-18 00:12:00 +0000 UTC",
	"2015-02-08 03:02:00 +0300 MSK m=+0.000000001",
	"2015-02-08 03:02:00.001 +0300 MSK m=+0.000000001",
	"2017-07-19 03:21:51+00:00",
	"2014-04-26",
	"2014-04",
	"2014",
	"2014-05-11 08:20:13,787",
	// yyyy-mm-dd-07:00
	"2020-07-20+08:00",
	// mm.dd.yy
	"3.31.2014",
	"03.31.2014",
	"08.21.71",
	"2014.03",
	"2014.03.30",
	//  yyyymmdd and similar
	"20140601",
	"20140722105203",
	// yymmdd hh:mm:yy  mysql log
	// 080313 05:21:55 mysqld started
	"171113 14:14:20",
	// unix seconds, ms, micro, nano
	"1332151919",
	"1384216367189",
	"1384216367111222",
	"1384216367111222333",

Plus,

1. Fixes bugs that happens you delete, update annotation.
2. Upgrades all dependencies

closes #20

Thanks!