Layer mouseover

HTML

<link rel="stylesheet" href="http://cdn.leafletjs.com/leaflet-0.7.3/leaflet.css">
<script src="http://cdn.leafletjs.com/leaflet-0.7.3/leaflet-src.js"></script>
<div id="map" ></div>

CSS

#map {
    height: 400px;
}

JavaScript

// geojson created with http://geojson.io/
var geojson = {
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      "geometry": {
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             ...