Bump version to 0.12.0 (#156)

Author: software-dov

setup.py

@@ -25,7 +25,7 @@
 
 setup(
     name='gapic-generator',
-    version='0.11.0',
+    version='0.12.0',
     license='Apache 2.0',
     author='Luke Sneeringer',
     author_email='lukesneeringer@google.com',