Add the missing shebangs and fix the wrong ones

I'm currently packaging puppetlabs-stdlib for Fedora / RHEL and rpmlint noticed several files missing shebangs. That resulted in many errors being thrown out and the impossibility for the package to be accepted into the official repositories.

It would be great if these changes could be reflected on the tarballs hosted at forge.puppetlabs.com, otherwise I can just rebase my work by creating a tarball from the master branch.

Thanks!