Import `reload` from `importlib` instead of `imp`

The `imp` module was deprecated in Python 3.4 in favor of `importlib`, and the function `imp.reload` is now just a wrapper for `importlib.reload`.

IPython/extensions/autoreload.py

@@ -121,9 +121,8 b' import traceback'
 import types
 import weakref
 import gc
-from importlib import import_module
+from importlib import import_module, reload
 from importlib.util import source_from_cache
-from imp import reload
 
 # ------------------------------------------------------------------------------
 # Autoreload functionality