grunt is a peer dependency.

Author: Grayside

package.json

@@ -4,7 +4,6 @@
   "version": "0.5.1",
   "main": "bootstrap.js",
   "dependencies": {
-    "grunt": "0.4.5",
     "grunt-available-tasks": "0.5.4",
     "grunt-composer": "0.4.4",
     "grunt-concurrent": "1.0.0",
@@ -26,6 +25,9 @@
     "lodash": "2.4.1",
     "time-grunt": "1.0.0"
   },
+  "peerDependencies": {
+    "grunt": ">= 0.4.5 < 0.5"
+  },
   "keywords": [
     "build",
     "drupal",