work around npm 5 behavior by installing appdmg at mac build time

Author: larrysalibra

package.json

@@ -13,7 +13,7 @@
     "test": "NODE_ENV=test ./node_modules/.bin/gulp test",
     "web": "NODE_ENV=production ./node_modules/.bin/gulp prod",
     "mac": "NODE_ENV=production ./node_modules/.bin/gulp mac",
-    "mac-release": "NODE_ENV=production ./node_modules/.bin/gulp mac-release",
+    "mac-release": "npm install --no-save appdmg && NODE_ENV=production ./node_modules/.bin/gulp mac-release",
     "dev": "NODE_ENV=development ./node_modules/.bin/gulp dev",
     "dev-ui": "echo 'Please use dev instead of dev-ui'",
     "dev-proxy": "NODE_ENV=development ./node_modules/.bin/gulp proxy"
@@ -163,9 +163,6 @@
     "triplesec": "^3.0.25",
     "zone-file": "^0.2.2"
   },
-  "optionalDevDependencies": {
-    "appdmg": "^0.4.5"
-  },
   "engines": {
     "node": ">=6",
     "npm": ">=5"