kijiproject.github.com: DOCS-130. First editing of setup section of Express userguide.

issue: https://jira.kiji.org/browse/DOCS-130
review: https://review.kiji.org/r/1319
commit: https://github.com/kijiproject/kijiproject.github.com/commit/a07114eea309c474824804f5d6a023591b7f13c1