WIP: GitLab.com vs GitLab CE vc GitLab EE

Closes blog-posts#264 (closed) and #797 (closed)

• General Feedback: too long? Too much info? Something missing?
• Tech review: Axil, Robert
• Product review: Amara, Chad
  • New outlines (structure): https://docs.google.com/a/gitlab.com/document/d/1DCaZsJ9NBMFb3r-H4b8nsnDgH1yJV7lfs-HIgMrSKls/edit?usp=sharing
• Content/English review: Erica
• Last pass (optional): Sean

Images (@lukebabb would you help me?):

• Cover
• Social media

Last check:

• File date
• Description

Let's make this post rock folks! 🚀 #teamwork

Publishing date: to be set