GMAP3 - Erro Uncaught ReferenceError: google is not defined

Estou tentando colocar um mapa no meu site usando o GMAP3 porem fica dando esse erro:

Uncaught ReferenceError: google is not defined              gmap.min.js:13

1. r @ gmap3.min.js:13 t.fn.gmap3 @ gmap3.min.js:13 (anonymous function) @ (index):145 x.Callbacks.l @ jquery-2.0.3.min.js:4 x.Callbacks.c.fireWith @ jquery-2.0.3.min.js:4 x.extend.ready @ jquery-2.0.3.min.js:4 S @ jquery-2.0.3.min.js:4

Função

    <script type="text/javascript">
      $(function(){
      
        $("#test1").gmap3({
          marker:{
            latLng: [-20.3118511,-40.3065644],
            options:{
              draggable:true
            },
            events:{
              dragend: function(marker){
                $(this).gmap3({
                  getaddress:{
                    latLng:marker.getPosition(),
                    callback:function(results){
                      var map = $(this).gmap3("get"),
                        infowindow = $(this).gmap3({get:"infowindow"}),
                        content = results && results[1] ? results && results[1].formatted_address : "no address";
                      if (infowindow){
                        infowindow.open(map, marker);
                        infowindow.setContent(content);
                      } else {
                        $(this).gmap3({
                          infowindow:{
                            anchor:marker, 
                            options:{content: content}
                          }
                        });
                      }
                    }
                  }
                });
              }
            }
          },
          map:{
            options:{
              zoom: 17,
             scrollwheel: false
    },
                scaleControl: true,
                panControl: false,
                navigationControl: false,              
                mapTypeId: 'roadmap',
                streetViewControl: false,
            }
          
        });
        
      });
 
               
        
                
                
    </script>

HTML:

   <div id="test1" class="gmap3"></div> 

CSS:

     .gmap3{
 height:400px;
 width: 100%;
    float:left;
      }



#gmap3-menu{
  background-color: #FFFFFF;
  width:170px;
  padding:0px;
  border:1px;
  cursor:pointer;
  border-left:1px solid #cccccc;
  border-top:1px solid #cccccc;
  border-right:1px solid #676767;
  border-bottom:1px solid #676767;
}
#gmap3-menu .item{
  font-family: arial,helvetica,sans-serif;
  font-size: 12px;
  text-align:left;
  line-height: 30px;
  border-left:0px;
  border-top:0px;
  border-right:0px;
  padding-left:30px;
  background-repeat: no-repeat;
  background-position: 4px center;
}
#gmap3-menu .item.itemA{
  background-image: url(images/icon_greenA.png);
}
#gmap3-menu .item.itemB{
  background-image: url(images/icon_greenB.png);
}
#gmap3-menu .item.zoomIn{
  background-image: url(images/zoomin.png);
}
#gmap3-menu .item.zoomOut{
  background-image: url(images/zoomout.png);
}
#gmap3-menu .item.centerHere{
  background-image: url(images/here.png);
}
#gmap3-menu .item.hover{
  background-color: #d6e9f8;
}
#gmap3-menu .item.separator{
  border-bottom:1px solid #cccccc;
}