Install wkhtmltox via rpm

Update wkhtmltopdf recipe for the 12.1 release.  (distributed as .rpm)

Add amd64 .rpms for centos5 and 6.

Debian and Ubuntu are not supported because `package` doesn't do dependency resolution on those platforms.  (That's what I was worried about when I pushed the first version.)  Using the `gdebi` cookbook might work, but I wasn't sure going down that route would be worth the effort.

Also note likely Amazon linux issue noted here:
https://github.com/sportngin-cookbooks/wkhtmltopdf/blob/wkhtmltox/attributes/default.rb#L12
Then if that is the case, then we should just kill it all together.  It is an extra 40MB we are adding as bloat to the repo that we just don't need, and when doing a git clone, that will add a significant amount of weight to the download.  Not fun when we are spinning up new server.

We might want to also consider a way of removing the old tarballs from the history once this is merged in.