Log Message:
Update ruby-octokit to 4.7.0.

4.7.0								2017/04/05

* #837 Fix passing options to all_organizations
* #841 Add new methods from the most recent org memberships API enhancements
* #851 Fix application requests for non dotcom hosts
* #858 Don't mutate the options variable passed to API calls
* #871 Add support to prerelease Integrations API
* #874 Handle PR Review errors
* #860 Implement Review Preview API
* #869 Use Organization.path for organization membership method
* #880 Fix incorrect mimetype for integrations in PREVIEW_TYPES
* #881 Change several occurrences of Hash#merge!