test key and .test accounts

[morgunder]

for live site testing i prefer to use .test in the email to signal sending emails through my mandrill test key.

for example: [email protected] will always be sent out through the mandrill test key even in a production environment.

is this something that other users of this package would like? can anyone make a pull request for this?

[dandv]

I've added tests to https://atmospherejs.com/wylio/mandrill. See #29.