Instructions for creating an OS X native development environment

Probably not 100% complete yet, but covers enough to pass all specs.

NOTE: requires either libXML2 2.7.6 or the separately submitted fix to
pretty_text_spec.rb
The wrong version actually got moved to this branch when I tried to clean some things up. This version should be correct :-)
replace CRLF with LF
prevent crlf on yml files
fix some typos in English strings
cs translation update
Post processing of images adds prefix second time when post processing a post with one or more images if running with a prefix
Fix for reply to user avatar and picture uploading not working when editing post with discourse running in a prefix
Sync folder now specifies id

Vagrant 1.1.5 seems to think we are overriding a previous shared folder
in our script. Passing the id solves this.
If an admin or moderator edits a visitor's post, the restrictions should be based
on the *editors* access rights, not the original poster.
Can change TOS content via site content editor
admins/moderators should not receive "body is too similar" when editing
a regular user's post.
Exclude recently made invisible topics from the categories list. Also remove a couple n+1 queries.
Fixes broken spec
1st child in post body blockquotes, no top margin
Replace MultisiteI18n hack with SiteContent and admin editing.
remove a bunch of unneeded font-awesome css
keep French l10n up to date
remove vendor prefixes from chosen CSS

we're modern baby
add text-align: center to header icons