v0.14.1: PSR-6 Support, PHP7 Improvements, and Prep for v1.0.0

v0.14.1

• Implemented PSR-6 interfaces.
• Removed Driver::setOptions($options) in favor of Driver::constructor($options)
• Removed deprecated DriverList::getDrivers function.
• Removed deprecated invalidation constants in the Item class.
• Removed SQLite Extension support (SQLite3 is still available).
• The set function no longer persists data.
• Removed expiration time for set function
• Added expiresAt and expiresAfter functions to the Item class.
• getExpiration to return current datetime when no record exists.
• Added save function to PoolInterface.
• Changed getItemIterator to getItems
• RuntimeException now extends from \RuntimeException
• Added isHit function to ItemInterface.
• Added the hasItem function to the Pool, which should mostly be avoided.
• Renamed Pool::purge to Pool::clear.
• Added Pool::deleteItem and Pool::deleteItems.
• Removed legacy methods for defining keys- keys must be defined as strings.
• Added support for "APCU" functions.
• Removed sqlite2 support (sqlite3 is still supported).