Update composer.json

Author: barryvdh

composer.json

@@ -17,7 +17,7 @@
         }
     ],
     "require": {
-        "php": ">=5.6",
+        "php": "^7",
         "psr/log": "^1.0",
         "symfony/var-dumper": "^2.6|^3|^4"
     },
@@ -36,7 +36,7 @@
     },
      "extra": {
         "branch-alias": {
-            "dev-master": "1.15-dev"
+            "dev-master": "1.16-dev"
         }
     }
 }