create plain_language_primer

First draft of an explanation of FOIA and the process behind it. Our hope is that this is a bit more approachable than most FAQs or primers out there. Borrowed heavily from the information on FOIA.gov.

Will need to be adjusted here and there.
Merge branch 'master' into plain_language_primer
update pages, turn the plain file into a markdown file
rename to learn.md
some copy edits, cc @rjmajma
Merge pull request #29 from 18F/plain_language_primer

create plain_language_primer
Update learn.md

Minor copyedits and clarifications!
Merge pull request #37 from corizarek/patch-1

Update learn.md
Fix a couple of tiny markdown errors, cc @corizarek
moving stuff around
Merge branch 'prototype' into requests

Conflicts:
	assets/css/main.css
	assets/css/pure-min-0.5.0.css
	css/main.css
	css/pure-min-0.5.0.css
	index.html
	public/css/main.css
	public/css/pure-min-0.5.0.css