remove yepnope

yepnope.js is deprecated and only around for archival purposes anymore. I'd say that's a good reason to remove it.

> Yepnope has been deprecated. There are new best practices that you should likely follow instead. Please read our notice here. We will keep these docs online for those still using the old version.
Merge pull request #79 from m90/patch-1

remove yepnope