v0.2.0

Changes summary:

• GRN inference step: multiprocessing is now used by default in place of dask to run GRNBoost2
• Images are now always pulled from DockerHub
• Requirements file updated
• New tiny test dataset (reduced run time) and test profile
• Additions to the PBMC10k tutorial (AUC threshold)
• Code and readme cleanup
• Additional (optional) parameter passes a fixed seed to the GRNBoost2 algorithm (e.g. --seed 777)