Report binary diff

If a diff contains binary files, it produces messages like:

```
diff --git a/screenshots/split-view.png b/screenshots/split-view.png
index 1c352c2..e1fb381 100644
Binary files a/screenshots/split-view.png and b/screenshots/split-view.png differ
```

It could be nice if `parse-diff` gives a `binary: true` flag in file object