Fix loading paginated content on IE

https://developer.mozilla.org/en-US/docs/Web/API/window.scrollY

> window.pageYOffset == window.scrollY; // always true
For cross-browser compatibility, use window.pageYOffset instead of window.scrollY.

Will fix #148

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The other change is a fix to [Ember Inspector](https://github.com/emberjs/ember-inspector), as it was throwing an error when attempting to inspect a `StoryController` of a `comment` type