`interdiff` not parsing patch with rename

[thejcannon]

Akin to #22, interdiff is choking on patchfiles continaing renames:

before.diff:

diff --git a/Lib/typing.py b/Lib/_typing.py
similarity index 100%
rename from Lib/typing.py
rename to Lib/_typing.py

(anything for after.diff)

$ interdiff -q before.diff after.diff`
interdiff: before.patch doesn't contain a patch
--- /dev/null
+++ b/Lib/typing.py
[...]