see: https://github.com/blog/738-sidejack-prevention-phase-2-ssl-everywhere

* simplifies some sentences
* use a more neutral language with less you/yours

Reason: Calling docrails a "branch" is fine, no need to change the terminology. It is a remote in my machine, and it has been called branch since the very beginning: http://weblog.rubyonrails.org/2008/5/2/help-improve-rails-documentation-on-git-branch

This reverts commit 35a266ed.

It turns out aptitude has been removed from Ubuntu 10.10
and while you can manually install it, apt-get is the
blessed package manager. Google for "aptitude removed
from Ubuntu" for more details. Thanks to Rafael Mendonça
França for pointing this out.

since a lot of people use Ubuntu, document specific aptitude calls for some C dependencies in the contrib guide

* adds instructions for PostgreSQL
* adds references to mysql2 here and there
* puts documentation contributions on par with code contributions
* adds a section about Rails Contributors
* documents C dependencies for Nokogiri and the database libs
* everything double-checked and revised step by step
* adds a section about warnings in the test suite
* removes section about the Rails wiki
* title and filename renamed
* overall rewording