message: Fixed incorrect example code
diff: @@ -266,12 +266,12 @@ Saving multiple Presentations:
  * In order to generate a new, unique Presentation just create a new instance of the library then add objects and save as normal.
  ```javascript
  -var pptx = new PptxGenJS();
  +var pptx = require("pptxgenjs");
  pptx.addNewSlide().addText('Presentation 1', {x:1, y:1});
  pptx.save('PptxGenJS-Presentation-1');
  // Create a new instance ("Reset")
  -pptx = new PptxGenJS();
  +pptx = require("pptxgenjs");
  pptx.addNewSlide().addText('Presentation 2', {x:1, y:1});
  pptx.save('PptxGenJS-Presentation-2');
  ```
  