j-card does not seem to work out of the box.

[Peppe]

I added j-card to my app:

<link rel="import" href="../../bower_components/j-elements/j-card.html">
...
<j-card>hello</j-card>

Then I checked the browser. J-card did not visually add anything. In the console there's an error:

Uncaught TypeError: Vaadin.ThemableMixin is not a function
    at j-card.html:198
    at j-card.html:265

and the row 198 is:

class CardElement extends Vaadin.ThemableMixin(Polymer.Element) {

[jouni]

Thanks for the report!

Fixed in 790b262 and 82018fc (I had forgotten a bunch of imports).