Hey!
First of all, really great, clean and promising project

But you have few dependencies which kind of breaking deal for small projects, like my:

• marshmallow and also I found some dependency on dotenv package https://github.com/sloria/environs/blob/master/environs/__init__.py#L16

Do you have any plans, or do you need any help with using python 3.7 typing system and throw marshmallow as a dependency?

With microservice infrastructure, when you have 3-4 dependencies in total, we would like not to use packages with some heavy external dependencies

Thank you