bump version to 0.8.0

there's a minor api change in #132 that may affect some users

src/tufup/__init__.py

@@ -5,7 +5,7 @@
 
 # https://packaging.python.org/en/latest/guides/single-sourcing-package-version/
 # https://semver.org/
-__version__ = '0.7.1'
+__version__ = '0.8.0'
 
 logger = logging.getLogger(__name__)