Truncate long names

Hey @solidsnack we were running into errors with zonify today because it was autogenerating cnames that were too long for AWS. I put in a bit of a hack to work around it and upgraded to your most recent version and discovered we also were getting errors from having too many records in our round robin cnames. I added another dirty fix for that one as well.

I am happy to clean this up if you give me some guidance as to how you'd like to see it incorporated, or if you think this is a reasonable approach we can just take it as is.