Resource queue
Mongo queue draft
Resource queue
Refactoring
Fix unit test failure
Merge branch 'queue'

Conflicts:
	.travis.yml
	composer.json
	composer.lock
	src/Valera/Resource.php
	src/Valera/Worker/HttpClient.php
	tests/Valera/Tests/ResourceQueue/AbstractTest.php
	tests/Valera/Tests/ResourceQueue/InMemoryTest.php
	tests/Valera/Tests/ResourceQueue/Pdo/AbstractTest.php
	tests/Valera/Tests/ResourceQueue/Pdo/MySQLTest.php
	tests/Valera/Tests/ResourceQueue/Pdo/SQLiteTest.php
	tests/Valera/Tests/ResourceTest.php
	tests/config.sample.php