Add curl as dependency

Author: webflo

composer.json

@@ -7,8 +7,9 @@
         "php": ">=5.4.5",
         "composer-plugin-api": "^1.0.0",
         "guzzlehttp/guzzle": "~6.1",
-        "codegyre/robo": "~0",
-        "pear/archive_tar": "~1.0"
+        "codegyre/robo": "^0.7.1",
+        "pear/archive_tar": "~1.0",
+        "ext-curl": "*"
     },
     "autoload": {
         "psr-4": {