dynamically use this template

[yakir12]

This is for an issue in skeleton.jl:
It would be great to be able generate the appveyor.yml (and actually the .travis.yml) file dynamically, so that if it changes here it's most current version gets used in the generated package (that's what skeleton does). So, is there some programmatic way to access the most resent version of the appveyor.ylm file? Right now its embedded in the README.md file, but it might be better if it was it's own file we could wget or something.