Issue #1475510 by timmillwood, hussainweb, davidwbarratt, alexpott, Mile23, pfrenssen, claudiu.cristea, webchick, catch, Crell, patcon, RobLoach, kim.pepper, dawehner, neclimdul, Mixologic, gagarine, sun, nod_, effulgentsia, drumm, Sylvain Lecoy, jhedstrom, katbailey, xjm, klausi, Seldaek, Barryvdh: Remove external dependencies from the core repo and let Composer manage the dependencies instead

(cherry picked from commit 2971d9c0)