Disable scroll wheel for zooming in favor of map zoom buttons

It's causing annoying behaviour for desktop users when scrolling
the page to the bottom and there is more content below the
map.

The behaviour of touchable devices does not seem to be
affected by this change and keeps behaving the same.

app/assets/javascripts/map.js

@@ -117,7 +117,7 @@
         return "<a href='/budgets/" + data.budget_id + "/investments/" + data.investment_id + "'>" + data.investment_title + "</a>";
       };
       mapCenterLatLng = new L.LatLng(mapCenterLatitude, mapCenterLongitude);
-      map = L.map(element.id).setView(mapCenterLatLng, zoom);
+      map = L.map(element.id, { scrollWheelZoom: false }).setView(mapCenterLatLng, zoom);
       App.Map.maps.push(map);
       L.tileLayer(mapTilesProvider, {
         attribution: mapAttribution