Sample run minor issue in README

[celstark]

The README lists this:
docker run -ti -v $PWD/ds114_test1:/home/jovyan/work/data bids/mindboggle /home/jovyan/work/data /home/jovyan/work/data/derivatives/ participant

Yet what I think you mean is:
docker run -ti -v $PWD/ds114_test1:/home/jovyan/work/data bids/mindboggle /home/jovyan/work/data /home/jovyan/work/data participant

The run.py file appends "derivatives" onto the output directory. So, as-written, it would go into work/data/derivatives/derivatives/mindboggle