Openlayers touch support

[karimbahgat]

It would be a great addition in efficiency and comfort to use mapwarper on touch devices, which is increasingly the case for many modern laptops. Currently the maps only respond to the mouse pointer.

My suspiscion is that the website currently uses an older version of OpenLayers. In the newest stable OpenLayers, 2.13.1, touch controls are automatically included when adding the NavigationControl to the map. So two things are needed:

• change all openlayers imports and update the openlayers static file to the newest from http://openlayers.org/two/
• make sure every map adds the navigation control (if that doesn't work add the touch navigation explicitly, see http://dev.openlayers.org/docs/files/OpenLayers/Control/TouchNavigation-js.html).

Doing this has the added benefit of giving the maps a more modern look.

I would have made a pull request, but unfortunately I don't know Ruby, and I wouldn't be able to test my changes locally to see if it works.

[karimbahgat]

This would also partly take care of #74 without breaking any dependencies or requiring major changes.