refactor: remove sync mode (#1141)

BREAKING CHANGE:

* Remove `sync` mode
* Remove TransitionStub
* Remove Transition

Author: eddyerburgh

package.json

@@ -36,7 +36,7 @@
     "babel-plugin-syntax-jsx": "^6.18.0",
     "babel-plugin-transform-decorators-legacy": "^1.3.4",
     "babel-plugin-transform-vue-jsx": "^3.7.0",
-    "babel-polyfill": "^6.23.0",
+    "babel-polyfill": "^6.26.0",
     "babel-preset-env": "^1.6.0",
     "babel-preset-flow-vue": "^1.0.0",
     "babel-preset-stage-2": "^6.24.1",

packages/create-instance/extract-instance-options.js

@@ -11,7 +11,6 @@ const MOUNTING_OPTIONS = [
   'attrs',
   'listeners',
   'propsData',
-  'sync',
   'shouldProxy'
 ]