Default the language to en - more useful for specs

app/assets/javascripts/locale/index.js

@@ -9,7 +9,7 @@ const locales = {
   en,
 };
 
-const lang = document.querySelector('html').getAttribute('lang');
+const lang = document.querySelector('html').getAttribute('lang') || 'en';
 
 export { lang };
 export default new Jed(locales[lang]);

spec/javascripts/cycle_analytics/limit_warning_component_spec.js

 import Vue from 'vue';
+import Translate from '~/vue_shared/translate';
 import limitWarningComp from '~/cycle_analytics/components/limit_warning_component';
 
+Vue.use(Translate);
+
 describe('Limit warning component', () => {
   let component;
   let LimitWarningComponent;