Update CHANGELOG.md

Merge pull request itay-grudev#97 from autoantwort/master

SingleApplication::currentUser and codecs

Merge pull request itay-grudev#96 from itay-grudev/primary_user

v3.1.0a Added primaryUser()

Merge pull request itay-grudev#76 from itay-grudev/android_fallback

Android and iOS fallback

Update CHANGELOG.md

Update CHANGELOG.md