Merge pull request #605 from mozilla/issue-587-change-default-lang

refactor(config): change default language to en-US rather than en

I dig it. No config updates for prod deployments. Thanks @zaach!

server/lib/configuration.js

@@ -109,7 +109,7 @@ var conf = module.exports = convict({
   i18n: {
     defaultLang: {
       format: String,
-      default: 'en'
+      default: 'en-US'
     },
     debugLang: {
       format: String,
@@ -118,7 +118,7 @@ var conf = module.exports = convict({
     supportedLanguages: {
       doc: 'List of languages this deployment should detect and display localized strings.',
       format: Array,
-      default: ['en', 'it-CH'],
+      default: ['en-US', 'it-CH'],
       env: 'I18N_SUPPORTED_LANGUAGES'
     },
     translationDirectory: {

server/lib/i18n.js

@@ -28,7 +28,7 @@ module.exports = function (config) {
   // stateful object with helper methods.
   var abideObj = abide.abide(
     {
-      default_lang: config.defaultLang,
+      default_lang: abide.localeFrom(config.defaultLang),
       debug_lang: config.debugLang,
       supported_languages: config.supportedLanguages,
       translation_directory: config.translationDirectory,