update to version 2.0.0 to break w/ the Python 2 version.

The API hasn't changed, but want to help prevent confusion.

setup.py

@@ -1,7 +1,7 @@
 from distutils.core import setup
 
 setup(name='pasn1',
-      version='1.0.1',
+      version='2.0.0',
       description='An ASN.1 encoder/decoder with json like interface.',
       author='John-Mark Gurney',
       author_email='jmg@funkthat.com',