kijiproject.github.com: DOCS-145. 'shell' is misspelled in two commands

issue: https://jira.kiji.org/browse/DOCS-145
review: https://review.kiji.org/r/1456
commit: https://github.com/kijiproject/kijiproject.github.com/commit/f4a6a090408826bbb0bc3e81c461eaf7ae11044a