Added subaccount support - https://mandrillapp.com/api/docs/subaccounts.JSON.html
Added subaccount support - https://mandrillapp.com/api/docs/subaccounts.JSON.html (gofmt)
Added subaccount support - https://mandrillapp.com/api/docs/subaccounts.JSON.html (remove comment)
Merge pull request #5 from jkassemi/master

Adds subaccount support