Foramontano/adding languages (#89)

- Doc that describes the steps to add a new language  to Spacedeck Open
- New file with translated entries for using in Spacedeck Open in Spanish
- Include 'es' as new locale in Spacedeck Open
- Include a radiobutton for users could select the new language

spacedeck.js

@@ -34,7 +34,7 @@ console.log("Booting Spacedeck Open… (environment: " + app.get('env') + ")");
 app.use(logger(isProduction ? 'combined' : 'dev'));
 
 i18n.expressBind(app, {
-  locales: ["en", "de", "fr", "oc"],
+  locales: ["en", "de", "fr", "oc", "es"],
   defaultLocale: "en",
   cookieName: "spacedeck_locale",
   devMode: (app.get('env') == 'development')