Move assetgraph-sprite and historgram to direct dependencies and node…

…-zopfli to devDependency

package.json

@@ -41,6 +41,7 @@
   ],
   "dependencies": {
     "assetgraph": "5.3.1",
+    "assetgraph-sprite": "^3.0.1",
     "bluebird": "^3.5.0",
     "browserslist": "4.2.1",
     "chalk": "^2.3.2",
@@ -49,6 +50,7 @@
     "estraverse": "^4.2.0",
     "express-processimage": "8.0.0",
     "extend": "^3.0.0",
+    "histogram": "^3.0.1",
     "jpegtran": "1.0.5",
     "lodash": "^4.14.1",
     "memoizesync": "1.1.1",
@@ -59,24 +61,20 @@
     "pngquant": "1.3.0",
     "urltools": "0.4.1"
   },
-  "optionalDependencies": {
-    "node-zopfli": "2.0.2"
-  },
   "devDependencies": {
     "autoprefixer": "^9.0.0",
-    "assetgraph-sprite": "^3.0.1",
     "coveralls": "^3.0.0",
     "eslint": "^5.0.0",
     "eslint-config-pretty-standard": "^2.0.0",
     "eslint-plugin-prettier": "3.0.0",
     "gettemporaryfilepath": "^1.0.0",
     "gifsicle-stream": "^0.3.0",
     "gm": "^1.21.1",
-    "histogram": "^3.0.1",
     "html-webpack-plugin": "^3.2.0",
     "jsdom": "^12.0.0",
     "less": "^2.7.1",
     "mocha": "^5.1.0",
+    "node-zopfli": "^2.0.2",
     "nyc": "^13.0.1",
     "prettier": "^1.13.5",
     "requirejs": "^2.3.3",