Extension should be checked from originalImage.
Don't leave leftover classes.
Limited Zepto support.

Requires Simply Deferred plugin and doesn't support
AMD for Zepto, since the library doesn't care about
AMD. Adding pseudo-definition to the code doesn't
make much sense.

Dense will never get any Zepto specific fixes,
so the plugin works as well as the Zepto API
handles things. Dense is not going to solve browser
specific compatibility issues for Zepto. Abstraction,
if necessary, needs to happen somewhere else.

As far as Zepto compatibility goes, the plugin does
somewhat work on the most up to date webkit
browsers. There might be some uncaught exceptions(?)
and the reported attributes are going to be different.

E.g. attr('width') will get '0' instead of undefined.