Replaced article with new text
Fix double space
Removed diagrams and replaced with bullet points

Bullet point sentences taken from David Cotterill's email.
Remove unused images
style guide – use a lead-in for bullets
style guide – don't use caps
Add fourth area

Following paragraph talks about 4 areas as described in linked blog post.
Merge pull request #277 from alphagov/tech-leader-job-descriptions

Replaced article with new text