Huge patch size

[9241304]

I'm trying to make patch for 2.7 MB files (executables). They are compiled at different time from the same sources by the same compiler, so they have the same size, but some different bytes (~100-200 bytes)
Original xdelta3 produces patch 100-200 bytes, but go-xdelta produces 1.4 MB patch using default block size (8MB) after possible fix of #9 (ignore EOF for source). I experimented with different block sizes, but minimum patch size still greater 15KB.