Add Amethyst.
Merge pull request #940 from ianyh/ianyh-amethyst

Add Amethyst.
Add Knox Cask

Knox lets you easily create, access, and backup encrypted file vaults.
These vaults are great for storing large number of files of any size:
confidential documents, images, source code, application data files,
customer information.
Merge pull request #941 from ohskylab/knox

Add Knox Cask