fixing a couple bugs related to parsing s3 file paths now that we have
two or even three md5 hashes.  Introducing the much discussed
filter_tagger_ids stage, which is now filtering out the serif-only
subcorpus, as described in
examples/streamcorpus-2014-v0_3_0-serif-only.yaml
Merge branch 'master' of github.com:trec-kba/streamcorpus-pipeline