In the current version, you can remove the app authorizations from Facebook and Twitter by visiting your settings on the respective services. 

Here's how the respective services enable you to remove the app and revoke authorization of the app.

Facebook: http://www.facebook.com/help/?faq=170585223002660 

Twitter: https://support.twitter.com/articles/76052-how-to-connect-and-revoke-third-party-applications 

We are currently working on making signing in, authorizing and removing the authorization easier in coming updates.