Update reserved extension.

Signed-off-by: crynobone <crynobone@gmail.com>
Allow to directly register an extension. Closes #46

Signed-off-by: crynobone <crynobone@gmail.com>
Merge branch '2.1' into 2.2

Signed-off-by: crynobone <crynobone@gmail.com>

Conflicts:
	src/Extension/Environment.php
	tests/FactoryTest.php