fixed issue #22: Possible wrong comparsion method inside getEdgeDefinition method

Author: fceller

src/main/java/com/arangodb/entity/EdgeDefinitionsEntity.java

@@ -79,7 +79,7 @@ public void addEdgeDefinition(EdgeDefinitionEntity edgeDefinition) {
    */
   public EdgeDefinitionEntity getEdgeDefinition(String collectionName) {
     for (EdgeDefinitionEntity edgeDefintion : this.edgeDefinitions) {
-      if (edgeDefintion.getCollection() == collectionName) {
+      if (edgeDefintion.getCollection().equals(collectionName)) {
         return edgeDefintion;
       }
     }