Added MIT license type to package.json

package.json

@@ -22,5 +22,6 @@
   },
   "main": "./lib/winston-mongodb",
   "scripts": { "test": "vows test/*-test.js --spec" },
-  "engines": { "node": ">= 0.4.0" }
+  "engines": { "node": ">= 0.4.0" },
+  "license": "MIT"
 }