Bump version to 1.20.0-dev (#50)

Signed-off-by: Uilian Ries <[email protected]>

Author: uilianries

patch_ng.py

@@ -29,7 +29,7 @@
     SOFTWARE.
 """
 __author__ = "Conan.io <[email protected]>"
-__version__ = "1.19.0"
+__version__ = "1.20.0-dev"
 __license__ = "MIT"
 __url__ = "https://github.com/conan-io/python-patch"