Add usage section to README.md

[seancomeau]

Running the client or server results in a failure to read the "servers file". A sample of this file as well as a more detailed explanation of the command line arguments would be helpful.

gen_file.py seems to generate some random files to serve, but it's not obvious what to do with them. What values should we choose for block size and chunks?

spawn_remote.py provides some clues, though it references stuff on your AFS we probably don't have access to.

Also add a link to your paper.

[kwonalbert]

i've added a readme with a bit more detail. let me know if something isn't clear or it doesn't work.