Promote TFP version from dev to stable

Author: csuter

tensorflow_probability/python/version.py

@@ -24,7 +24,7 @@
 # stable release (indicated by `_VERSION_SUFFIX = ''`). Outside the context of a
 # release branch, the current version is by default assumed to be a
 # 'development' version, labeled 'dev'.
-_VERSION_SUFFIX = 'dev'
+_VERSION_SUFFIX = ''
 
 # Example, '0.4.0-dev'
 __version__ = '.'.join([