Explain in README that ACM certificate needs to be in us-east-1
Explain in README that ACM certificate needs to be in us-east-1

Cloudfront, as a global (non-region) service, requires the certifcates to be setup in the us-east-1 region. This changes the README.md to explicitly state that.
scoates/Zappa,scoates/Zappa,Miserlou/Zappa,pjz/Zappa,Miserlou/Zappa,pjz/Zappa