RELI release v0.90

Add CWL workflow; update README

- fix minor typo in numbered list of arguments during RELI execution

- preserve sample output in a separate directory

- move 'output' directory from example/example_run.sh to top level

- bring in CWL workflow using weirauchlab/reli:latest Docker image

- add 'exclean' target to 'make help' target (clean up output files from
  example analysis run

- closes #12 (no mention of CWL in README)