Remove old field-mount and field-change emitters and listeners.

Replace FormMixin with new functionality.

js/components/checkbox_input.js

@@ -1,5 +1,3 @@
-import { emitEvent } from '../lib/emitters'
-
 export default {
   name: 'checkboxinput',
 
@@ -15,22 +13,9 @@ export default {
     }
   },
 
-  created: function() {
-    emitEvent('field-mount', this, {
-      optional: this.optional,
-      name: this.name,
-      valid: this.optional || this.isChecked,
-    })
-  },
-
   methods: {
-    onInput: function(e) {
+    onInput: function() {
       this.$parent.$emit('field-change')
-      emitEvent('field-change', this, {
-        value: e.target.checked,
-        name: this.name,
-        valid: this.optional || this.isChecked,
-      })
     },
   },