Bump version to 4.20.0

Author: rmk135

docs/main/changelog.rst

@@ -7,8 +7,8 @@ that were made in every particular version.
 From version 0.7.6 *Dependency Injector* framework strictly 
 follows `Semantic versioning`_
 
-Development version
--------------------
+4.20.0
+------
 - Add container "self" injections.
   See issue: `#364 <https://github.com/ets-labs/python-dependency-injector/issues/364>`_.
   Thanks to `@shaunc <https://github.com/shaunc>`_ for suggesting the feature.

src/dependency_injector/__init__.py

@@ -1,6 +1,6 @@
 """Top-level package."""
 
-__version__ = '4.19.0'
+__version__ = '4.20.0'
 """Version number.
 
 :type: str