Move npm-run-all to devDependencies

Author: nodaguti

package.json

@@ -26,7 +26,6 @@
   "homepage": "https://github.com/nodaguti/textlint-rule-write-good",
   "repository": "nodaguti/textlint-rule-write-good",
   "dependencies": {
-    "npm-run-all": "^1.6.0",
     "textlint-rule-helper": "^1.1.5",
     "write-good": "^0.9.1"
   },
@@ -38,6 +37,7 @@
     "eslint": "^2.5.1",
     "eslint-config-airbnb": "^6.2.0",
     "mocha": "^2.4.5",
+    "npm-run-all": "^1.6.0",
     "power-assert": "^1.3.1",
     "textlint": "^6.0.3",
     "textlint-tester": "^1.2.0"