removed unused package

Author: moizKachwala

package.json

@@ -25,7 +25,6 @@
     "es6-promise": "^3.2.1",
     "es6-shim": "^0.35.1",
     "express": "^4.13.4",
-    "gulp-concat": "^2.6.0",
     "mongoose": "^4.5.0",
     "reflect-metadata": "^0.1.2",
     "rxjs": "^5.0.0-beta.6",