We have three or four different introduction sentences to the guides.
After this commit, we use the same one everywhere.

Talked with @fxn about this. Bullet points should have periods at the ends.

This reverts commit f5b9ed4f.

REASON: Translation work can not be done in the docrails repository

In Textile `*` would convert to `<strong>`, but in Markdown we have to
use `**` instead.

- Cases in point - GitHub, Git, Twitter and Rails should start
  with capitals when used outside code context
- Pro Git found - URL has been updated for its new home
- Faces for links - More descriptive titles on link prompt
  instead of "here"

This is the last chapter before I go back and make sure the guide is
complete/review

We no longer go through all the files and  frameworks that are required
by Rails. Instead we will only focus on the code that gets executed as
well as important concepts.

We will no longer cover every single file that is loaded by Rails, as
this would be too difficult and time consuming to maintain.

We also expect the reader to know about rails server at this point.

* update rails versions
* remove outdated code snippets
* few more corrections

This guide is currently a wip and pending reviews. [ci skip]