Implement a "Submit a blog post" feature

[ossanna16]

Implement a feature in the side bar for people to submit blog posts for blog.pinaxproject.com.

The inspiration for this came from the Django Girls blog

When clicking on the "Submit a blog post" button, the user should get to a page where they can submit their blog post and edit it in Markdown, like so

In order to submit a post the user would need an account for blog.pinaxproject.com without admin access.
Everyone with admin access to blog.pinaxproject.com should then be able to see the submitted post, make further edits and publish the post as they see fit.

For further discussion on this topic, please join the #blog-pinaxproject-com channel in our Slack channel. @jtauber is happy to provide input and guidance.

[ossanna16]

Do you think this would be a good issue for someone wanting to start contributing to Pinax?