kiji-express: EXP-417. Rewrite express bash script as python script

issue: https://jira.kiji.org/browse/EXP-417
review: https://review.kiji.org/r/1678
commit: https://github.com/kijiproject/kiji-express/commit/8aab907dbd581c8185ef52e78280ce4db9a4f527