chore(package): update lockfile

https://npm.im/greenkeeper-lockfile

Author: greenkeeperio-bot

yarn.lock

@@ -4006,9 +4006,9 @@ preserve@^0.2.0:
   version "0.2.0"
   resolved "https://registry.yarnpkg.com/preserve/-/preserve-0.2.0.tgz#815ed1f6ebc65926f865b310c0713bcb3315ce4b"
 
-prettier@1.7.4:
-  version "1.7.4"
-  resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.7.4.tgz#5e8624ae9363c80f95ec644584ecdf55d74f93fa"
+prettier@1.8.1:
+  version "1.8.1"
+  resolved "https://registry.yarnpkg.com/prettier/-/prettier-1.8.1.tgz#91064d778c08c85ac1cbe6b23195c34310d039f9"
 
 pretty-format@^21.2.1:
   version "21.2.1"
@@ -5313,7 +5313,7 @@ vinyl@^0.5.0:
     clone-stats "^0.0.1"
     replace-ext "0.0.1"
 
-"vm2@github:patriksimek/vm2#custom_files":
+vm2@patriksimek/vm2#custom_files:
   version "3.5.0"
   resolved "https://codeload.github.com/patriksimek/vm2/tar.gz/7e82f90ac705fc44fad044147cb0df09b4c79a57"