Bypass EULA on DMG file when installing

I've added a new provider `appdmg_eula_charles` to the module, and switched the package provider for Charles to use this.

I've named it `appdmg_eula_charles` so that it doesn't conflict with the `appdmg_eula` provider I'll submit to the boxen module. This means users won't be required to upgrade their version of the boxen module to install Charles.