Add Charter, source: practicaltypography.com
Merge pull request #247 from jgill/font-charter

Add Charter, source: practicaltypography.com
Add Gentium Plus Cask
use new header form in `font_casker` devscript
use new header form in docs
new-style header in font-abeezee
new-style header in font-abel
new-style header in font-aboriginal-sans
new-style header in font-aboriginal-serif
new-style header in font-abril-fatface
new-style header in font-aclonica
new-style header in font-acme
new-style header in font-actor
new-style header in font-adamina
new-style header in font-adinatha-tamil-brahmi
new-style header in font-advent-pro
new-style header in font-aegean
new-style header in font-aegyptus
new-style header in font-african-sans
new-style header in font-african-serif