Fix dependency categorization

Author: jakezatecky

package.json

@@ -35,6 +35,7 @@
     "eslint-plugin-jsx-a11y": "^3.0.2",
     "eslint-plugin-react": "^6.9.0",
     "gulp": "^3.9.1",
+    "gulp-autoprefixer": "^3.1.1",
     "gulp-eslint": "^3.0.1",
     "gulp-header": "^1.8.8",
     "gulp-mocha-phantomjs": "^0.12.0",
@@ -46,8 +47,5 @@
     "react-dom": "^15.3.0",
     "webpack": "^1.13.1",
     "webpack-stream": "^3.2.0"
-  },
-  "dependencies": {
-    "gulp-autoprefixer": "^3.1.1"
   }
 }