Fix cassette module to work with py34

vcr/cassette.py

@@ -16,11 +16,13 @@ from .util import partition_dict
 
 try:
     from asyncio import iscoroutinefunction
-    from ._handle_coroutine import handle_coroutine
 except ImportError:
     def iscoroutinefunction(*args, **kwargs):
         return False
 
+if sys.version_info[:2] >= (3, 5):
+    from ._handle_coroutine import handle_coroutine
+else:
     def handle_coroutine(*args, **kwags):
         raise NotImplementedError('Not implemented on Python 2')