Add documentation for new features in v1.7.1

[tannerdolby]

Fields to document:

• [x] minified
• [x] custom
• [x] css
• [x] js
• [x] inline_css
• [x] inline_js
• [x] audio
• [x] video
• [x] determiner
• [x] og_secure_img_url
• [x] og_img_type