I would assume you would have to use subdirectories (but there may be a simpler way):
/index.html => http://jasonhoffmann.github.io
/contact/index.html => http://jasonhoffmann.github.io/contact
However, you may have more control using CNAME to redirect the GitHub page to your own domain. Sorry I don't have a definite answer for you, but hopefully this can get you started.
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