Make compatible with many python versions

Author: dlski

README.md

@@ -1,5 +1,6 @@
 # python-mediator
-Elastic and extensible asyncio CQRS python microframework.
+Elastic and extensible asyncio CQRS + ES python microframework.
+Compatible with recent python versions: 3.7, 3.8, 3.9.
 
 Corresponds to clean architecture patterns, ideal for
 command/query segregation scenarios and event-driven design approaches.

pyproject.toml

@@ -6,7 +6,7 @@ authors = ["Damian Łukawski <damian@lukawscy.pl>"]
 license = "MIT"
 
 [tool.poetry.dependencies]
-python = "^3.8"
+python = ">=3.7 <3.10"
 
 [tool.poetry.dev-dependencies]
 black = "^20.8b1"
@@ -17,6 +17,7 @@ flake8-black = "^0.2.1"
 pytest = "^6.1.0"
 coverage = "^5.4"
 pytest-asyncio = "^0.14.0"
+importlib_metadata = { version = "^3.7.0", python = "~3.7" }
 
 [build-system]
 requires = ["poetry>=0.12"]