Add all languages listed on locale as supported languages.

Fixes bug 1013278

.env-dist

@@ -1,2 +1,5 @@
 # Choose a port
 PORT=5000
+
+# i18n Language Support
+export SUPPORTED_LANGS='[ "*" ]'

app.js

@@ -28,7 +28,7 @@ var healthcheck = {
 
 // Setup locales with i18n
 app.use( i18n.middleware({
-  supported_languages: [ 'en-US' ],
+  supported_languages: env.get("SUPPORTED_LANGS"),
   default_lang: 'en-US',
   mappings: require('webmaker-locale-mapping'),
   translation_directory: path.resolve(__dirname, 'locale')