Removed 'actions' from Vuex.Store constructor (#210)

This is the only place in the documentation where `actions` are passed in to `new Vuex.Store`. There is no explanation for the discrepancy (i.e. all other documentation, including the API and the next page dedicated to actions, indicate those should be passed to the Vue constructor.

docs/en/mutations.md

@@ -130,7 +130,6 @@ import { SOME_MUTATION } from './mutation-types'
 
 const store = new Vuex.Store({
   state: { ... },
-  actions: { ... },
   mutations: {
     // we can use the ES2015 computed property name feature
     // to use a constant as the function name