Update README to contain pure Markdown
Update README to contain pure Markdown

jshoyer/plantcv,jshoyer/plantcv,danforthcenter/plantcv,AntonSax/plantcv,AntonSax/plantcv,stiphyMT/plantcv,stiphyMT/plantcv,stiphyMT/plantcv,danforthcenter/plantcv,danforthcenter/plantcv