Changed findElement to avoid having to put the selectors of every pare…

[diego-fernandez-santos]

I would like a solution compatible with my application loaded like SHADY or SHADOW.

To do that we need a more flexible selector strategy in which one we don't have to put the selectors of every parent web-component. In this way I would like to make the tests much less coupled with the internal structure of the web components.

For example, in the following page: `

.. `

Currently, to select the anchor, you have to use the "shop-app shop-homeshop-button a" selector.

But with this patch, you can just simple use "shop-button a" or "shop-app shop-button a" like valid selectors.