mandrill does not add DOCTYPE anymore.
integrate changes from James Cooper@Staffis.

Thanks James!
Reintegrate changes from MrTravisB

- SORRY!
Removing omitempty for TrackOpens and TrackClicks to make sure the values are transferred to mandrill as false and not omitted. This is because mandrill seems to default to true for these values, and if they are omitted there is no way to turn off click tracking.
Merge pull request #8 from hwsoderlund/master

Removing omitempty for TrackOpens and TrackClicks
Put id and rejected reason back in send message response
Merge pull request #9 from MrTravisB/master

Put id and rejected reason back in send message response
implemented lists/list method. Spec: http://apidocs.mailchimp.com/api/2.0/lists/list.php
fix lists/list endpoint
Merge pull request #10 from zacg/master

Implemented lists/list
implemented templates/list spec: http://apidocs.mailchimp.com/api/2.0/templates/list.php
fix json tags
Merge pull request #11 from zacg/master

Implemented templates/list
Support for Subaccounts when sending Mandrill Messages
Merge pull request #12 from sdrew/subaccount-send

Support for Subaccounts when sending Mandrill Messages
Add campaign create and send
Disable debug
Merge pull request #13 from kyleconroy/master

Add CampaignSend and CampaignCreate
fix constant formatting
Merge pull request #14 from enahs/patch-1

fix constant formatting