Fix Travis builds

Test on PHP 7 and 5.6

composer.lock

@@ -4,8 +4,8 @@
         "Read more about it at https://getcomposer.org/doc/01-basic-usage.md#composer-lock-the-lock-file",
         "This file is @generated automatically"
     ],
-    "hash": "b012f269a785a013725ff7f6cbf59df3",
-    "content-hash": "6745f521db34e3a535092cab5eec8afc",
+    "hash": "a16b07104a463e2beb02558d3c6d97b1",
+    "content-hash": "ed2f2e09c9147797cc42a8ffb8d878bb",
     "packages": [
         {
             "name": "aura/session",
@@ -1425,8 +1425,8 @@
             "name": "rg3/youtube-dl",
             "version": "2016.09.08",
             "dist": {
-                "type": "tar",
-                "url": "https://github.com/rg3/youtube-dl/archive/2016.09.08.tar.gz",
+                "type": "zip",
+                "url": "https://github.com/rg3/youtube-dl/archive/2016.12.18.zip",
                 "reference": null,
                 "shasum": null
             },