Add server options to "Creating" page

[iangilman]

In addition to listing tools that create zoomable images, we should add a list of servers that can serve zoomable images, including:

• http://iipimage.sourceforge.net/
• https://medusa-project.github.io/cantaloupe/

...to this page:

http://openseadragon.github.io/examples/creating-zooming-images/

[kittarlin]

Page update in progress.

[iangilman]

This has been fixed by #179.