tests: Use dealoc(element) for elements created with $compile()

[ThomasBurleson]

To address potential memory leaks within the Karma tests, use:

var $compile, scope, element;

afterEach(function() {
    dealoc(element);
  });

  function injectScopeAndCompiler() {
    return inject(function(_$compile_, _$rootScope_) {
      $compile = _$compile_;
      scope = _$rootScope_;
    });
  }

  function compileElement(inputHtml) {
    element = $compile(inputHtml)(scope);
    scope.$digest();
  }