Add extractor stage that takes yaml/tsv list of files as input
Add pdf to text transform stage
Add docx to text transform stage
Merge branch 'master' of https://github.com/trec-kba/streamcorpus-pipeline
renaming extractor --> reader one more (trivial)
Wrap conversions in try/except
Revise input format following discussion with John/Steve
Merge pull request #1 from luac/master

New pipeline stages