Make Phalcon\Logger\Adapter::commit() clear the queue

Fix #1742
Test case for #1742
Update CHANGELOG
Merge pull request #1748 from sjinks/issue-1742

Make Phalcon\Logger\Adapter::commit() clear the queue
Constant-time string comparison in Phalcon\Security::checkHash()

Fix #1755
Updated CHANGELOG
Phalcon\Security::deriveKey()

Generate a PBKDF2 key derivation of a supplied password
Test case
Optimization
Code fixes for PHP 5.6-dev and 5.7-dev
Updated CHANGELOG
Phalcon\Forms\Form::hasMessagesFor() should return boolean

Fix #1764
Optimize Phalcon\Forms\Form::getMessagesFor()
Helper for Phalcon\Validation\Message\Group::__construct()
Optimize Phalcon\Forms\Form::getMessages()
Validate parameters in Phalcon\Forms\Form::setEntity()
Optimize Phalcon\Forms\Form::add()
Optimize Phalcon\Forms\Form::render()
Optimize Phalcon\Forms\Form::get()
Optimize Phalcon\Forms\Form::label()