Delete the previous Layer and Modal
#937 Convert ch.onImageLoads into a static method
#923 Positioner must be a Constructor Function.
#938 Viewport: It should emit scroll and resize events.
#939 The widgets should emit and listen to an event when the layout was changed.
#941 EventEmitter: Migrate to prototype.
GH-889 GH-890 Zoom: inherit from popover and migrate to prototype.
Merge with Hernan
Merge with guille
GH-942 Collapsible: Return the instance on _show() and _hide().
GH-882 Popover: Don't reset the title nor alt attributes if it don't exists on the trigger.
#846 Dropdown should be a popover and inherit from Layer.
#845 Expandable should use this.name instead 'expandable'.
#882 Layer should close widgets with the same name as its constructor.
GH-882 Popover: Get content from the href if trigger is a link or action if trigger is a form.
GH-882 Popover: get the trigger feature into a prototype method
Merge with llinares
Use this. instead of  private variable.
privates methods template.update() and template.create() moved to prototype
#940 Store widgets into private members.