Fix for issue #1575, preview not showing updates

I'm not certain this is the same problem from #1575...? I wasn't able to reproduce it following those instructions, but maybe I misunderstood.

With a new post, I could enter content, tap Preview, and get the showSimplePreview, then go back, add more, and simple preview would show updates okay.

As soon as I tried to edit any saved post (published or draft) I could no longer see updates in the preview, because it would always do the showRealPreview.

I think ```[self.apost hasChanges]``` is supposed to be ```hasChanged```, and that fixes this. Or, I found a slightly different bug and #1575 is something different that I couldn't reproduce. :)