Merge branch 'develop'

* develop:
  First implementation in topojson.
Merge branch 'develop'

* develop:
  Fix the jekyll configuration options.
Merge branch 'develop'

* develop:
  Add a tooltip in the small multiple.
  Fix the footer link to github.
  Fix the page title.
Merge branch 'master' into gh-pages

* master:
  Add a tooltip in the small multiple.
  Fix the footer link to github.
  Fix the page title.
Add google analytics tracking id.
Merge branch 'gh-pages' into develop

* gh-pages:
  Add google analytics tracking id.