fix(applications-settings): Edit of application settings not working (#169)

PUT need to be used instead of POST
See: https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/api/settings.md

Author: max-wittig

src/services/ApplicationSettings.js

@@ -6,7 +6,7 @@ class ApplicationSettings extends BaseService {
   }
 
   edit(options) {
-    return RequestHelper.post(this, 'application/settings', options);
+    return RequestHelper.put(this, 'application/settings', options);
   }
 }