setup.py: Bump version to 0.13.0.beta1

Author: ix5

setup.py

@@ -18,7 +18,7 @@
 
 setup(
     name='isso',
-    version='0.13.0-dev',
+    version='0.13.0.beta1',
     author='Martin Zimmermann',
     author_email='[email protected]',
     packages=find_packages(),