Bump version to 4.2.0

docs/main/changelog.rst

@@ -7,6 +7,11 @@ that were made in every particular version.
 From version 0.7.6 *Dependency Injector* framework strictly 
 follows `Semantic versioning`_
 
+4.2.0
+-----
+- Add support of Python 3.9.
+- Update readme.
+
 4.1.8
 -----
 - Update asyncio daemon, single- and multi-container examples to use ``Resource`` provider.

src/dependency_injector/__init__.py

@@ -1,6 +1,6 @@
 """Top-level package."""
 
-__version__ = '4.1.8'
+__version__ = '4.2.0'
 """Version number.
 
 :type: str