add monolog for debugging

composer.json

@@ -1,28 +1,29 @@
 {
-    "name": "dilab/resumable.php",
-    "description": "PHP package for Resumable.js",
-    "authors": [
-        {
-            "name": "xu ding",
-            "email": "thedilab@gmail.com"
-        }
-    ],
-    "require": {
-      "php": ">=5.3.0",
-      "cakephp/filesystem": "^3.0"
-    },
-    "require-dev": {
-      "phpunit/phpunit": "~4.0"
-    },
-    "license": "MIT",
-    "autoload": {
-      "psr-4": {
-        "Dilab\\": "src/"
-      }
-    },
-    "autoload-dev": {
-      "psr-4": {
-        "Dilab\\Test\\": "test/src/"
-      }
+  "name": "dilab/resumable.php",
+  "description": "PHP package for Resumable.js",
+  "authors": [
+    {
+      "name": "xu ding",
+      "email": "thedilab@gmail.com"
     }
+  ],
+  "require": {
+    "php": ">=5.3.0",
+    "cakephp/filesystem": "^3.0"
+  },
+  "require-dev": {
+    "phpunit/phpunit": "~4.0",
+    "monolog/monolog": "^1.17"
+  },
+  "license": "MIT",
+  "autoload": {
+    "psr-4": {
+      "Dilab\\": "src/"
+    }
+  },
+  "autoload-dev": {
+    "psr-4": {
+      "Dilab\\Test\\": "test/src/"
+    }
+  }
 }