title: Vuex - Computed property "name" was assigned to but it has no setter
body: <p>I have a component with some form validation. It is a multi step checkout form. The code below is for the first step. I'd like to validate that the user entered some text, store their name in the global state and then send then to the next step. I am using <a href="https://github.com/baianat/vee-validate" rel="noreferrer">vee-validate</a> and vuex</p>
  
  <pre class="lang-html prettyprint-override"><code>&lt;template&gt;
  &lt;div&gt;
      &lt;div class='field'&gt;
          &lt;label class='label' for='name'&gt;Name&lt;/label&gt;
          &lt;div class="control has-icons-right"&gt;
  
              &lt;input name="name" v-model="name" v-validate="'required|alpha'" :class="{'input': true, 'is-danger': errors.has('name') }" type="text" placeholder="First and Last"&gt;
              &lt;span class="icon is-small is-right" v-if="errors.has('name')"&gt;
                  &lt;i class="fa fa-warning"&gt;&lt;/i&gt;
              &lt;/span&gt;
          &lt;/div&gt;
          &lt;p class="help is-danger" v-show="errors.has('name')"&gt;{{ errors.first('name') }}&lt;/p&gt;
  
      &lt;/div&gt;
      &lt;div class="field pull-right"&gt;
          &lt;button class="button is-medium is-primary" type="submit" @click.prevent="nextStep"&gt;Next Step&lt;/button&gt;
      &lt;/div&gt;
  &lt;/div&gt;
  &lt;/template&gt;
  
  &lt;script&gt;
  export default {
      methods: {
          nextStep(){
              var self = this;
  
              // from baianat/vee-validate
              this.$validator.validateAll().then((result) =&gt; {
                  if (result) {
                      this.$store.dispatch('addContactInfoForOrder', self);
                      this.$store.dispatch('goToNextStep');
                      return;
                  }
              });
          }
      },
      computed: {
          name: function(){
              return this.$store.state.name;
          }
      }
  }
  &lt;/script&gt;
  </code></pre>
  
  <p>I have a store for handling order state and recording the name. Ultimately I would like to send all of the info from multi step form to the server.</p>
  
  <pre class="lang-js prettyprint-override"><code>export default {
    state: {
      name: '',
    },
  
    mutations: {
      UPDATE_ORDER_CONTACT(state, payload){
        state.name = payload.name;
  
      }
    },
  
    actions: {
      addContactInfoForOrder({commit}, payload) {
        commit('UPDATE_ORDER_CONTACT', payload);
      }
    }
  }
  </code></pre>
  
  <p>When I run this code I get an error that <code>Computed property "name" was assigned to but it has no setter.</code></p>
  
  <p>How do I bind the value from the name field to the global state? I would like this to be persistent so that even if a user goes back a step (after clicking "Next Step") they will see the name they entered on this step</p>