export '__version__' in top-level module

This is so that all of fontmake's dependencies export a top-level
'__version__' string, following PEP 396 recommendation.

googlefonts/fontmake#251
googlefonts/fontmake#310

Author: anthrotype

Lib/booleanOperations/__init__.py

@@ -1,6 +1,7 @@
 from __future__ import print_function, division, absolute_import
 from .booleanOperationManager import BooleanOperationManager
 from .exceptions import BooleanOperationsError
+from .version import __version__
 
 # export BooleanOperationManager static methods
 union = BooleanOperationManager.union