Fix bug where a wildcard origin served over https would become https://*

The FF CDN fonts issue this solves had eaten away a few hours of my day today ... until I finally found your gem! Super useful, thanks!

I have an app that uses precompiled assets on Heroku served over SSL and CloudFront. When I first deployed with default settings, I noticed the origin was being set to https://*. I fixed it temporarily in the current version of the gem by configuring an explicit origin uri. This pull request allows the precompiled SSL scenario to work by default without any additional configuration.