Add a UITableView category for dynamically sizing cell heights using autolayout.

- Needs documentation
Fix issues with stories not being updated after a refresh

- Stories are now properly reloaded after a refresh

- Switch to using the UITableView+DynamicSizing category

- Make the fetched results controllers lazy
Switch to the UITableView+DynamicSizing category
Remove the token for keeping track of the story request; it is internal to MITNewsViewController and shouldn't be here.
Fixes the display of updated story objects
Fix several warnings regarding unused synthesized ivars