Instead of using 1 dictionary for all index paths we use N dictionaries with N being the number of sections.

We were looking if the numberOfStoryHeights > numberOfStoriesForCategoryInSection but all categories do not have the same number of stories.

Fixed #165 #166.
Removed cached heights that are not in tableview after reload.
initialize dictionary with nil
Fixed iOS 8 middle arrow popover.
Fix for corner cases.
We want the size of the image to matches the pixel-based dimensions of the image.   Source: UIImage Class Reference
Moved images to correct directory and added a read me.
Tweak wording of popover image readme.
Set the correct frame and bounds before adding constraints.

Fixes #202.
Merge pull request #187 from MIT-Mobile/3.6/ipad-mit-popover

Fix for MIT Popover not displaying correctly on iOS 8. Fixed #185
Merge pull request #168 from MIT-Mobile/3.6/ipad-news-estimatedHeightForRowAtIndexPath

3.6/ipad news estimated height for row at index path. Fixes #166
Merge branch 'refs/heads/3.6/ipad-news' into 3.6/ipad-news-categories