Bump required php to 7 and branch to 2.0

composer.json

@@ -13,7 +13,7 @@
         }
     ],
     "require": {
-        "php": ">=5.3.0",
+        "php": ">=7.0.0",
         "psr/log": "~1.0"
     },
     "require-dev": {
@@ -54,7 +54,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "1.18.x-dev"
+            "dev-master": "2.0.x-dev"
         }
     },
     "scripts": {