Add GeneralName and SubjectAlternativeName classes
diff --git a/setup.py b/setup.py
index d8c0790..60e6b78 100644
--- a/setup.py
+++ b/setup.py
@@ -43,6 +43,9 @@
 if sys.version_info < (3, 4):
     requirements.append("enum34")
 
+if sys.version_info < (3, 3):
+    requirements.append("ipaddress")
+
 if platform.python_implementation() != "PyPy":
     requirements.append(CFFI_DEPENDENCY)