fix: pin prettier version

Author: yyx990803

package.json

@@ -57,7 +57,7 @@
     "merge-source-map": "^1.1.0",
     "postcss": "^6.0.20",
     "postcss-selector-parser": "^3.1.1",
-    "prettier": "^1.13.7",
+    "prettier": "1.13.7",
     "source-map": "^0.5.6",
     "vue-template-es2015-compiler": "^1.6.0"
   }

yarn.lock

@@ -3544,7 +3544,7 @@ preserve@^0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/preserve/-/preserve-0.2.0.tgz#815ed1f6ebc65926f865b310c0713bcb3315ce4b"
 
-prettier@^1.13.7:
+prettier@1.13.7:
   version "1.13.7"
   resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.13.7.tgz#850f3b8af784a49a6ea2d2eaa7ed1428a34b7281"