add license for composer

composer.json

@@ -3,7 +3,8 @@
     "type":         "library",
     "description":  "lazy PHP5 library that provides Repositories as filesystem abstraction layer",
     "keywords":     ["file", "repository", "filesystem", "media", "abstraction"],
-    "require": {
+	"license": "MIT",
+	"require": {
         "php": ">=5.3.2",
 	    "aws/aws-sdk-php": "2.2.0",
 	    "symfony/yaml": "2.2",