Modify the newsletter title as it is published to reflect the date
Code style tweaks
Remove unneeded coded confusing the newsletter date situation
Use the newsletter title as the subject of the email
Sanitize email before passing it to wp_mail()
Document our wp_insert_post_data() function
Be explicit about the post type required for the modification of post data
Escape data before including it in the email
Remove the old single template for newsletters

We don't have a reason for a different single page template now that the preview is handled in the admin screen.
Take away all routes to viewing a newsletter on the front end

These are email newsletters, announcements can be viewed in the specific archives
Fill in the blanks on documentation
Additional marker that _generate_html_email() is private
Big spacing modifications to the HTML email template
Pull in the HTML email header image dynamically
Abstract standard font properties a bit in the HTML email
Tag v1.1 for push to production