unset = function() {
          if (view.hasPlaceholderSet()) {
            view.clear();
          }
          dom.removeClass(view.element, CLASS_NAME);
        }
Simulate HTML5 placeholder attribute

Needed since
   - div[contentEditable] elements don't support it
   - older browsers (such as IE8 and Firefox 3.6) don't support it at all

@param {Object} parent Instance of main wysihtml5.Editor class
@param {Element} view Instance of wysihtml5.views.* class
@param {String} placeholderText

@example
   wysihtml.dom.simulatePlaceholder(this, composer, "Foobar");