[WIP] Reword tutorial

Same content, but better wording. Highlights:

* No initial header. Chapters don’t start with two headers.
* Recommend _Ruby in Twenty Minutes_ over _Programming Ruby_. The later is old and ugly.
* Add recommendation for a CLI crash course.
* Decrease “bear with us” attitude. The purpose of the files and directories after `create-site` are explaned right away, for instance. Also, the 

To do:

* Finish rewording the tutorial, obviously.
* Play around with other markup languages. I am liking DocBook (but not the toolchain around it).
* Highlight identifiers more, because it is a common source of confusion.

Still a **work in progress** as I have only redone the first few sections.

CC @bobthecow @opensourcegrrrl