mustache.github.com -> mustache.github.io

[zane]

Hello,

Thank you for your work on this package!

I noticed there are a few references to mustache.github.com in the README and the About section, but it appears Github would prefer them to be mustache.github.io

[Kelli Johnson]

@shuckle16 I noticed one in ad91c14 of pull request #43. Let me know if there are more and I can add them to my pull request.