Loosen version requirements for pytz and jsonschema
Description of change
As discussed here in #123, a more permissive versioning is required to make singer-python compatible with Airflow.
Additionally, I personally have a project that requires some timezone updates present in pytz 2019.3. I've kept the allowed versions to a restricted range due to singer's preference for restrictive deps.
Manual QA steps
Risks
Rollback steps
- revert this branch
+1 on this
+1 these version pins can make life with singer-python difficult
this branch is out of date. I would be willing to make a new PR if there is interest in reviewing and merging it?
I've rebased this branch of master. Let me know if there's anything else that needs to be done.