Prevent Gmail clipping email

[jaydson]

From Mailchimp documentation:

When Gmail clips the message, it also clips the tracking code that accounts for opens. To make sure all opens are tracked, and your full campaign content isn't hidden behind a link, it is important to make your message smaller than 102KB

The newsletter tool should warn the editor about the content size.
Perhaps a HTML counter or something similar.

[jaydson]

For this one we'll need to incorporate some kind of "real" Mailchimp template as we need to count all html entities, including the template.