removal of "data-" attributes

I'm currently using the Google Maps Javascript API to add a map to our wesbite and I'm trying to get it to sit within the CKEditor code on the website. The only problem is, when I enter this:

<div class="googlemap" data-address="{ADDRESS HERE}" data-marker="true" data-icon="/Images/map-pointer.png" style="width:100%;height:300px;"></div>

But when it loads up in CKEditor it turns it into this:

<div class="googlemap" style="width:100%;height:300px;">&nbsp;</div>

How do I make it keep the "data-" attributes so I don't lose the map each time I load and save it?

Thanks