Markdown fixes for developer setup

This branch contains several Markdown-related fixes for the developer setup instructions, including:

1. Proper order of headings
2. Alignment of pre blocks within bulleted lists
3. Unordered list under Fedora changed into an ordered list (as it contains steps
4. Removal of `postgresql` and `postgresql-libs` as they're pulled in as dependencies anyway — this allows all the lines in that pre block to be shorter (as comments are aligned), so that lines do not wrap
Yeah we should add a  "TODO" or something under the Mac section.
 On Nov 21, 2014 12:33 PM, "Garrett LeSage" <notifications@github.com>
wrote:

> In developer_setup.md:
>
> >
> >  ### Mac
> >
> >
> > -## Setup Git and Github
> > +#### Setup Git and Github
>
> If that's the case, it shouldn't be under a blank "Mac" heading.
>
> —
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> <https://github.com/ManageIQ/guides/pull/43/files#r20728777>.
>