The reason why you cannot sign your app with your provisioning profile is because the application identifiers don't match. Your app's id is com.RememberStuff.RememberStuff while your provisioning profile is provisioned for apps with id com.rememberstuff.*. As Apple have stated in their documentation, the app identifier is case sensitive:
"However, unlike domain names, bundle IDs are case sensitive. If the App ID is lowercase, your bundle ID needs to be lowercase, too."
Change your app identifier to com.rememberstuff.RememberStuff and you should be able to sign and build it with AppBuilder.
Let me know if this works for you.