Restructures the post editor to work around some memory issues.

Fixes #1231 
Removes the UITableView. UITextView will handle the text sizing and scrolling on its own.
Title text field and options buttons are now subviews of the textView to retain the scroll behavior we want.
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See the commentary on the issue for background. 
One TODO for this patch is to mimic a detail disclosure icon in the Options button. If we're happy with the approach I'll add that to this PR before merging.