chore(06-02): download and include Action Scheduler library

- Downloaded Action Scheduler 3.9.3 from GitHub
- Placed in vendor/action-scheduler/ directory
- Included in main plugin file before other code for proper initialization
- Library will auto-initialize itself when required

vendor/action-scheduler/lib/cron-expression/README.md

@@ -0,0 +1,92 @@
+PHP Cron Expression Parser
+==========================
+
+[![Latest Stable Version](https://poser.pugx.org/mtdowling/cron-expression/v/stable.png)](https://packagist.org/packages/mtdowling/cron-expression) [![Total Downloads](https://poser.pugx.org/mtdowling/cron-expression/downloads.png)](https://packagist.org/packages/mtdowling/cron-expression) [![Build Status](https://secure.travis-ci.org/mtdowling/cron-expression.png)](http://travis-ci.org/mtdowling/cron-expression)
+
+The PHP cron expression parser can parse a CRON expression, determine if it is
+due to run, calculate the next run date of the expression, and calculate the previous
+run date of the expression.  You can calculate dates far into the future or past by
+skipping n number of matching dates.
+
+The parser can handle increments of ranges (e.g. */12, 2-59/3), intervals (e.g. 0-9),
+lists (e.g. 1,2,3), W to find the nearest weekday for a given day of the month, L to
+find the last day of the month, L to find the last given weekday of a month, and hash
+(#) to find the nth weekday of a given month.
+
+Credits
+==========
+
+Created by Micheal Dowling. Ported to PHP 5.2 by Flightless, Inc.
+Based on version 1.0.3: https://github.com/mtdowling/cron-expression/tree/v1.0.3
+
+Installing
+==========
+
+Add the following to your project's composer.json:
+
+```javascript
+{
+    "require": {
+        "mtdowling/cron-expression": "1.0.*"
+    }
+}
+```
+
+Usage
+=====
+```php
+<?php
+
+require_once '/vendor/autoload.php';
+
+// Works with predefined scheduling definitions
+$cron = Cron\CronExpression::factory('@daily');
+$cron->isDue();
+echo $cron->getNextRunDate()->format('Y-m-d H:i:s');
+echo $cron->getPreviousRunDate()->format('Y-m-d H:i:s');
+
+// Works with complex expressions
+$cron = Cron\CronExpression::factory('3-59/15 2,6-12 */15 1 2-5');
+echo $cron->getNextRunDate()->format('Y-m-d H:i:s');
+
+// Calculate a run date two iterations into the future
+$cron = Cron\CronExpression::factory('@daily');
+echo $cron->getNextRunDate(null, 2)->format('Y-m-d H:i:s');
+
+// Calculate a run date relative to a specific time
+$cron = Cron\CronExpression::factory('@monthly');
+echo $cron->getNextRunDate('2010-01-12 00:00:00')->format('Y-m-d H:i:s');
+```
+
+CRON Expressions
+================
+
+A CRON expression is a string representing the schedule for a particular command to execute.  The parts of a CRON schedule are as follows:
+
+    *    *    *    *    *    *
+    -    -    -    -    -    -
+    |    |    |    |    |    |
+    |    |    |    |    |    + year [optional]
+    |    |    |    |    +----- day of week (0 - 7) (Sunday=0 or 7)
+    |    |    |    +---------- month (1 - 12)
+    |    |    +--------------- day of month (1 - 31)
+    |    +-------------------- hour (0 - 23)
+    +------------------------- min (0 - 59)
+
+Requirements
+============
+
+- PHP 5.3+
+- PHPUnit is required to run the unit tests
+- Composer is required to run the unit tests
+
+CHANGELOG
+=========
+
+1.0.3 (2013-11-23)
+------------------
+
+* Only set default timezone if the given $currentTime is not a DateTime instance (#34)
+* Fixes issue #28 where PHP increments of ranges were failing due to PHP casting hyphens to 0
+* Now supports expressions with any number of extra spaces, tabs, or newlines
+* Using static instead of self in `CronExpression::factory`