fix(util): Correct CallActivities rendering

CallActivities aren't expanded by default the behavior can be set by 'di.isExpanded'

close  #131

lib/util/Di.js

@@ -5,5 +5,12 @@ module.exports.isExpandedPool = function(semantic) {
 };
 
 module.exports.isExpanded = function(semantic) {
-  return !semantic.$instanceOf('bpmn:SubProcess') || semantic.di.isExpanded;
-};
+
+  // Is type expanded by default?
+  var isDefaultExpanded = !(semantic.$instanceOf('bpmn:SubProcess') || semantic.$instanceOf('bpmn:CallActivity'));
+
+  // For non default expanded types -> evaluate the expanded flag
+  var isExpanded = isDefaultExpanded || semantic.di.isExpanded;
+
+  return isExpanded;
+};