…reventDefault call by default

Calling the `preventDefault` method every time on Click will change the behavior for all components and we don't want that because we will be breaking all existing behaviors.

I'm also changing the demo to listen for the `handleClick` event, it is called internally due to the explicit listener added in the component but its name is changed due to the ClayComponent implementation.

fix(clay-link): listens for the `handleClick` event and removes the preventDefault call by default

…e-variables.scss` should be Sass partials. The CSS equivalent shouldn't be created since these files are only meant to be consumed by `.scss` files."

This reverts commit 5d33765.

fix(clay-css): Revert "fix(clay-css): `atlas-variables.scss` and `bas…