Add base ebook generator using ebook-convert
Add option cover for ebook generation
Add command "ebook" to generate an ebook
Add format ebook to README.md
Merge pull request #42 from GitbookIO/feature/ebook

Fix #10: Add generation to ebook
Fix overflow on languages page
Remove need for README.md for multi-languages
Fix progress link to README
Add new lateral navigations
Improve new navigation on mobile
Fix display of table in page body
Don't use caching for search index
Center images in markdown body
Bump version to 0.1.2
Make use of github optional
Whoops, missed a couple of extra uses of githubId
Fixes --githubHost option for use with Github Enterprise.
Merge pull request #51 from calmdev/fix/gh-enterprise

Fixes --githubHost option for use with Github Enterprise.
Tidy up use of github, and make error more descriptive
Fix URL rewriting error on empty URLs

Fixes #54, fixes #59