title: jvectormap how to keep the current color when region is selected?
body: <p>Here is my problem, i have a scale of colors for different countries. When I select a country, its color change and I don't want to.</p>
  
  <p>I just want to use the stroke attribute (without the fill attribute) to display selected regions.</p>
  
  <p>Problem is that the default color for fill is "yellow". I tried to set the fill attribute for selected region to "none" but it erases my current color when selected.</p>
  
  <p>Have you guys a way to solve this issue?</p>
  
  <pre><code>        $('#worldMap').vectorMap({
          map: 'world_mill_en',
          series: {
              regions: [{
                  scale: ['#C1E712', '#5F7209'],
                  values: countryHitCounts,
              }]
          },
          regionStyle: {
              selected: {
                  fill: &lt;= is there a keyword to not change the color when selected??
                  stroke: 'red',
                  "stroke-width": 1,
              },
          },
          regionsSelectable: true,
          selectedRegions: countrySelected,
          onRegionSelected: function (event, code, isSelected, selectedRegions) {
                 //some code...
          },
      });
  </code></pre>
  
  <p>EDIT: in the minify js code source file, I changed the default style for selected region.
  <em>selected:{fill:"yellow"}</em> by <em>selected:{}</em>
  It works but if you have a better solution without changing the source file, I take it.</p>