warcio check/test should know about transfer encoding vs. digest computation issue

[wumpus]

Brought up in issue https://github.com/webrecorder/warcio/issues/74, it appears that most tools and the WARC standard disagree about how to compute digests when there is a transfer-encoding (i.e. chunked). "warcio check" should be extended to compute both digests and make useful comments about the situation.