Upgrade to Laravel 5.3
This change offers an incremental framework upgrade from 5.2 to 5.3.
The last 5.x version is 5.8, and Laravel 6 has been released,
but as the Laravel documentation offers migration paths by
minor version, upgrades will be incremental.
Test Plan: The test suite pass.
Reviewed By: dereckson
Maniphest Tasks: T1484
Differential Revision: https://devcentral.nasqueron.org/D2129