feat(bpmnrenderer): add conditional flow markers

See #29

lib/draw/BpmnRenderer.js

@@ -125,6 +125,26 @@ function BpmnRenderer(events, styles, bpmnRegistry, pathMap) {
           'stroke-width': 1,
           'stroke-dasharray': '1,0'
         }));
+
+    addMarker('conditional-flow-marker',
+      paper
+        .path('M 0,0 7.089123,3.1832974 0.00383366,6.1129516 -7.0814464,3.1832966 z')
+        .attr({
+          'fill': 'white',
+          'stroke': 'Black'
+        })
+        .marker(0, 0, 15, 15, 0, 0)
+        .attr({
+          markerUnits: 'strokeWidth',
+          markerWidth: 14.296,
+          markerHeight: 7.238,
+          orient: 'auto',
+          overflow: 'visible',
+          'stroke-width': 1,
+          'stroke-dasharray': '1,0',
+          'refX': -8,
+          'refY': 3.15
+        }));
   }
 
   function drawCircle(p, width, height, offset) {
@@ -1046,6 +1066,12 @@ function BpmnRenderer(events, styles, bpmnRegistry, pathMap) {
     'bpmn:SequenceFlow': function(p, data) {
       var polyline = drawLine(p, data.waypoints);
 
+      if(!!bpmnRegistry.getSemantic(data.id).conditionExpression) {
+        polyline.attr({
+          'marker-start': marker('conditional-flow-marker')
+        });
+      }
+
       return polyline.attr({
         'marker-end': marker('sequenceflow-end')
       });