Reverse the transaction instruction order.

Early decisions cause later ones through dependencies. So in order to
perform the earlier decisions the later ones must be fulfilled first.

src/Composer/DependencyResolver/Solver.php

@@ -836,7 +836,7 @@ class Solver
             );
         }
 
-        return $transaction;
+        return array_reverse($transaction);
     }
 
     protected $decisionQueue = array();