message: handle installation similair to Vuex
diff: @@ -3,12 +3,19 @@ import makeMixin from './mixin';
  import makeDirective from './directive';
  import ErrorBag from './errorBag';
  import Rules from './rules';
  -import { assign } from './utils';
  +import { assign, warn } from './utils';
  import defaultOptions from './config';
  import mapFields from './helpers';
  -// eslint-disable-next-line
  -const install = (Vue, options) => {
  +let Vue;
  +
  +const install = (_Vue, options) => {
  + if (Vue) {
  + warn('already installed, Vue.use(VeeValidate) should only be called once.');
  + return;
  + }
  +
  + Vue = _Vue;
  const config = assign({}, defaultOptions, options);
  if (config.dictionary) {
  Validator.updateDictionary(config.dictionary);
  