move 'official' version number to Cython/__init__.py to avoid importing the...

move 'official' version number to Cython/__init__.py to avoid importing the complete compiler package for a version check

Cython/Compiler/Version.py

-version = '0.13'
+# for backwards compatibility
+
+from Cython import __version__ as version

Cython/__init__.py

-from Compiler.Version import version as __version__ 
+__version__ = '0.13'
 
 # Void cython.* directives (for case insensitive operating systems). 
 from Cython.Shadow import *

setup.py

@@ -197,7 +197,7 @@ except ValueError:
 
 setup_args.update(setuptools_extra_args)
 
-from Cython.Compiler.Version import version
+from Cython import __version__ as version
 
 setup(
   name = 'Cython',