Update ol

This PR updates ol to https://github.com/openlayers/ol3/commit/757ccf148b8303fab7cea068b35cc41f0111bca5. This is to have the new ol.View2D#getZoom function, that we will use not to have to pass view resolutions to the map directive.

This PR also adds ol-simple.js, which we can use for the tests. See #111.

Please review.