Write use case example

[bheavner]

Get a toy RNA-seq data set on S3 somewhere publicly accessible. 1)Make a bag from that, (bag also exists on S3, I guess?) and 2) give it an identifier. Ideally, I'd like to 3) send the bag to Globus to run FASTQC on it, generating a set of output files (I don't know if I can do that with just identifier, or how bag is passed, exactly).. 4) make/get a bag of those outputfiles and 4) give them an identifier to share with a collaborator.