Merge pull request #1489 from Unity-Technologies/release-v0.6-tick-version

tick the version number

ml-agents/setup.py

 
 setup(
     name='mlagents',
-    version='0.5.0',
+    version='0.6.0',
     description='Unity Machine Learning Agents',
     long_description=long_description,
     long_description_content_type='text/markdown',