Add lesson on how to tidy in tidy-data/01-tidy

I had the impression that other, existing content in the Data Carpentry materials discussed delimited files -- what they are and, perhaps, how to export an Excel file to tab or comma delimited. But I wasn't sure of the very best place to link to. 

I share a couple of slides with @cbahlai earlier about that topic, so I could link to that if there's nothing better within the repo:
http://www.slideshare.net/jenniferbryan5811/excel-readwritedelimfiles