chore(package): update shelljs to version 0.7.4

https://greenkeeper.io/

Author: greenkeeperio-bot

package.json

@@ -25,7 +25,7 @@
   "dependencies": {
     "debug": "2.2.0",
     "lodash": "4.13.1",
-    "shelljs": "0.7.0",
+    "shelljs": "0.7.4",
     "write-json-file": "2.0.0"
   }
 }