Revert "ignore en_US in i18n - GH-1905 & GH-1675"

This reverts commit f65ee501.

lib/i18n.js

@@ -70,9 +70,7 @@ exports.abide = function (options) {
       json_exists: path.existsSync(json_file_path(l)),
       gt: null
     };
-    // english translations are broken and not maintained, hence the second part of
-    // this if statement - see issue #1912
-    if (l !== debug_locale && l !== 'en_US') {
+    if (l !== debug_locale) {
       if (! mo_cache[l] || ! mo_cache[l].mo_exists || ! mo_cache[l].json_exists) {
         var msg = util.format('Bad locale=[%s] file(s) do not exist [%s] or [%s]. See locale/README',
                               l, mo_file_path(l), json_file_path(l));
@@ -114,8 +112,7 @@ exports.abide = function (options) {
     resp.local('format', format);
     req.format = format;
 
-    // ignore translation files in en_US - see issue #1905
-    if (mo_cache[locale].mo_exists && locale != 'en_US') {
+    if (mo_cache[locale].mo_exists) {
       if (mo_cache[locale].gt === null) {
         mo_cache[locale].gt = new Gettext();
         var mo_path = mo_file_path(locale);