uninstalled pass gets locally deleted

[patroqueeet]

when Apple APNS service returns 410 while trying to send a push notification, our local db might be outdated. hence we must delete the local registration.

• added code
• added tests
• updated changeme/release notes/readme

addresses #38

[patroqueeet]

@NachE @alexandernst ready for review. anything I missed? may I quickly ask you to see the async code? not very confident here...

[patroqueeet]

@NachE @alexandernst can above threads get marked as resolved? what else needs to be done to get read-to-merge state?

[alexandernst]

I think we're good to go! @patroqueeet wanna do the honors and merge?

[patroqueeet]

@NachE @alexandernst merged. should we push a new version?

[alexandernst]

Done :)