Don't set pjax.state unless options.push or options.replace is true

Our premise is this: if the pjax call has both `push` and `replace` set to false, the call shouldn't swap out the `pjax.state`. This is a degenerate use of `pjax` but it's surprising behavior from the standpoint of expecting to degenerate toward basic Ajax behavior.

Here's a scenario where we're getting into trouble with the current implementation:

Have this HTML:

```html
<html>
<head>...</head>
<body>
  <div id="navigation">

</body>
</html>
```