Add rimraf to dev-dependencies to pass build.

Author: Ethan Cohen

package.json

@@ -32,7 +32,8 @@
     "coveralls": "^2.11.8",
     "eslint": "^2.2.0",
     "istanbul": "^1.0.0-alpha.2",
-    "mocha": "^2.4.5"
+    "mocha": "^2.4.5",
+    "rimraf": "^2.5.2"
   },
   "engines": {
     "node": ">=0.10.0"