Adds locale switcher js code + feature tests

app/assets/javascripts/locale_switcher.js.coffee

@@ -0,0 +1,19 @@
+App.LocaleSwitcher =
+
+  href_with_params: (query_params) ->
+    loc = window.location
+
+    loc.protocol + "//" + loc.hostname +
+      (if loc.port then ':' + loc.port else '') +
+      loc.pathname +
+      loc.hash +
+      '?' + $.param(query_params)
+
+  initialize: ->
+    $('.js-locale-switcher').on 'change', ->
+      query_params = window.getQueryParameters()
+      query_params['locale'] = $(this).val()
+      window.location.assign(App.LocaleSwitcher.href_with_params(query_params))
+
+
+