fix incorrect dependency type for phantomjs

package.json

@@ -5,8 +5,7 @@
   "author": "Declan de Wet <declandewet@me.com>",
   "bugs": "https://github.com/declandewet/vue-meta/issues",
   "dependencies": {
-    "deepmerge": "^1.2.0",
-    "phantomjs-prebuilt": "^2.1.13"
+    "deepmerge": "^1.2.0"
   },
   "devDependencies": {
     "babel-cli": "^6.18.0",
@@ -31,6 +30,7 @@
     "karma-phantomjs-launcher": "^1.0.2",
     "karma-webpack": "^1.8.0",
     "mocha": "^3.1.2",
+    "phantomjs-prebuilt": "^2.1.13",
     "rimraf": "^2.5.4",
     "rollup": "^0.36.3",
     "rollup-plugin-buble": "^0.14.0",

yarn.lock

@@ -3772,7 +3772,7 @@ pend@~1.2.0:
   version "1.2.0"
   resolved "https://registry.yarnpkg.com/pend/-/pend-1.2.0.tgz#7a57eb550a6783f9115331fcf4663d5c8e007a50"
 
-phantomjs-prebuilt@^2.1.13, phantomjs-prebuilt@^2.1.7:
+phantomjs-prebuilt, phantomjs-prebuilt@^2.1.7:
   version "2.1.13"
   resolved "https://registry.yarnpkg.com/phantomjs-prebuilt/-/phantomjs-prebuilt-2.1.13.tgz#66556ad9e965d893ca5a7dc9e763df7e8697f76d"
   dependencies: