Here comes the TestFlight workflow we all have been waiting for. :-)
You can list your team members, invites (with invite status) and apps. (Apps require the Area 51 feature that can be enabled here).
You can send an invitation to a given email directly from Alfred, and you can copy your API token.
To setup after installation, right-click the workflow and select "Show in Finder".
Open the file "login.sh".
Enter your login info into the variables "USERNAME" and "PASSWORD".
Done!
Download it here