Javascript stimulates named parameters with objects.
The previous version used `ciphertext` to denote
the usable result from a call to `encrypt`.
However, this caused some cogitative load.
Ciphertext is used to denote encrypted data,
however the result of a call to `encrypt` in not _only_ encrypted data.
The AWS Encryption SDK uses envelop encryption,
so the result of a call to `encrypt` include not only the encrypted data,
but also, the encrypted data keys, metadata, and the encryption context.
By returning both the `messageHeader` *and* the `ciphertext`
users are confused about what exactly was *in* `ciphertext`.
This is compounded by returning `messageHeader`
which is just a parsed version of the header
that is already returned by the result of `encrypt`

The named parameter is now call `result`.
This makes it clear that this is the important return value from `encrypt`
that is the only value needed for `decrypt`.