v0.54.0

* Pin troposphere version and update to 3.x (zappa#1029)
* Relax stage name restrictions when not using apigateway (zappa#993)
* Wait for lambda to become active during deploy/update (zappa#992)
* add support for Python 3.9 (zappa#1026)

Merge pull request zappa#967 from ian-whitestone/add-docker-support

Update/deploy a lambda using a Docker container image