Clarify $.extend's use

Removes the `options` var that received the output of the `$.extend`
function. This was unnecessary because the `options` var is not used
again.
Removes custom selector portion of the plugin.

Unnecessary for this plugin.
Shortcode replacement works

Shortcode is replaced with all images returned at the moment. Shortcode
is also probably fairly brittle.
Comment out qunit testing

I don’t know how it works right now, so it’s gone until I have the time.
features for initial release ready
Adjust Bower so jQuery is dependency, not dev.
change description
remove qunit from grunt default for now
Update README, build minified, bump version