Update README.md
Revert "Revert "started on STDIN functionality, removed support for multiple files (csvkit will do handle this)""

This reverts commit 422d2907ae651c1564addee819a5e0453d47f14e.
Merge branch 'stdin_funcs' of github.com:datamade/dedupe-csv into stdin_funcs
Got STDIN working if you've already got training data
piping in and out works... on unix systems
Update README.md
Update README.md
Update README.md
if no outputfile defined output to stdout
fix tests
Merge pull request #14 from datamade/stdin_funcs

Dedupe now takes stdin and can write to stdout, on unix derived OS, closes #4