I also think `cask-filename` should become `cask--filename`. Projects (like [pallet](https://github.com/rdallasgray/pallet)) should use the `cask-file` function over the constant. I know I came across an issue discussing this, but cannot find it ATM.

/cc @rdallasgray because of [pallet.el#L87](https://github.com/rdallasgray/pallet/blob/9bb599fa9db251ec08c92a52c9165743f5375579/pallet.el#L87)