Image picker not updating properly after changing image

When you use `getImage` it triggers the image picker to appear. Hovering over reveals a set of images, and clicking on an image updates the text in the code to refer to that image. However, when you move the mouse away (`mouseleave`), the small popup still shows the previous image.

I made a quick fix that hides it altogether on the `mouseleave` event, but I imagine the preferred behavior is to have the updated image show in the small tooltip (which matches the behavior of the parameter tooltip).

In any case, here's what it currently looks like: http://screencast.com/t/RJDom3Z3RaA

I'll make some tweaks soon hopefully to have it update the `currentTooltip` to reflect the newly selected image.

Start at the getImage image-picker flow and trace how selecting an image updates the code and how mouseleave controls the small popup. Compare that behavior with the parameter tooltip; done means the popup shows the newly selected image after the mouse leaves, or follows the agreed hide behavior.

Written by the indexing model from the issue text.