Export and document html5lib.__version__

It's not much use if it's private.

Author: twm

html5lib/__init__.py

@@ -19,7 +19,8 @@
 from .serializer import serialize
 
 __all__ = ["HTMLParser", "parse", "parseFragment", "getTreeBuilder",
-           "getTreeWalker", "serialize"]
+           "getTreeWalker", "serialize", "__version__"]
 
 # this has to be at the top level, see how setup.py parses this
+#: Distribution version number, which asymptotically approaches 1.
 __version__ = "0.9999999999-dev"