I knew since the beginning that I had to comply with best practices and provide my website over a secure channel. Not that there is much to hide in a static, open source website, but at least this part of your surf will stay private (within limits).
This website is now stored on S3, but served though the CDN AWS Cloudfront which provides the (free) HTTPS certificate.
As a side note, I would like to thank everyone at Travis for this amazing service. It is extremely easy to configure and the github integration is top-notch!