Meaningful diff-replacement for binary files

Hi there,

classic text-based diffs are not meaningful for binary files.

Bitbucket only displays a message to that effect.

But actually, there are alternatives.

My proposal is to display the output of some common hashing mechanisms (both before and after) for these files.

My favorite list:

1. md5 (for conveninence, not security)
2. sha-2256
3. (some variant of) visualHostKey (as implemented by ssh)