Reloaded elements are not loaded lazily

[ericstratmann]

Expected Behavior

When enableAutoReload=true and a data attribute changes on an element that had been previously loaded, the element should not be reloaded until it is in the viewport.

Current Behavior

When the element's data attribute changes, lozad immediately reloads the element even when not in the viewport.

Possible Solution

The mutation callback could check if the element is visible. If it is, it calls load as it does currently. Otherwise, it sets the data-loaded attribute to false.

Steps to Reproduce (for bugs)

1. Create a new lozad observer with enableAutoReload: true
2. Lazy load an image by moving it on screen
3. Move the image off screen
4. Change the data-src attribute on the element
5. Notice that the src attribute has changed on the element despite not being in the viewport.