Update about.gitlab.com homepage

Goal: Update about.gitlab.com to create a homepage that showcases one GitLab vs. the various product lines.

Homepage should answer:

• Who/what is GitLab (GitLab is an integrated solution for the full software development lifecycle. (we should say this in a more fun/quirky way.)
• Explain our product (would be good to structure as code test deploy and highlight noteworthy features and mention our integrations as both GitHub and BitBucket highlight key integrations.)
• Highlight some noteworthy attributes of the company and its products (e.g. vision, release cadence, open development)
• Share customer testimonials and case studies