Move common method for a CapsuleManager to trait, this would reduce the requirement to produce new CapsuleManager for other component in the future (e.g: laravel/framework#5032)

Also remove duplicate "require-dev" component (when already explicitly declare in "require").

Signed-off-by: crynobone <crynobone@gmail.com>
Add test for CapsuleManagerTrait and fixes a typo.

Signed-off-by: crynobone <crynobone@gmail.com>
Cleaning up a few things. Merging.