Add new posts from railsgirls.com.
Update Rails Install Guide with upstream.
Update GitHub guide.
Update commenting guide.
Update design guide.
Update resizing with carrierwave guide.
Update devise guide.
Update Heroku Guide.
Update EngineYard Guide.
Update design using html and css guide.
Update Testing with RSpec guide.
First pass of app guide.
Change wording of translated by.
Update index page.

* New structure.
* Hide contents that has no translation.
* 4 spaces indent of HTML.
Update link of logo.
Lack of db:migrate, update commenting guide.
Use bootstrap 3 as the railsgirls.com already did that.
Revert root route.
Add note about recreate versions. Update some code snippets (thumbnails).
Update mini_magick to 3.7.0.