Revert "Bump Octokit"

This reverts commit 6bf694a0cf000d66206509be2b3ee791f5b2bf6f.
Merge branch 'master' of https://github.com/boxen/boxen
Bump Octokit to 2.3.0

Fixes #111. Octokit >= 2.2 does not blow up when accessing missing resource
attributes. Octokit >= 2.3 is Ruby 1.8.7 compatible.
Merge pull request #116 from boxen/fix-null-email-issue

Fix null email issue