added SDExpandingTableViewController and example

TODO: need to determine if UIPopoverController is still limiting width to < 600px.  The restriction seemed to go away in iOS 5ish, but the docs still say width should be < 600.
fixed copyrights, added @required to protocols.
Merge pull request #89 from setdirection/SDExpandingTableViewcController

added SDExpandingTableViewController and example
Merge remote-tracking branch 'upstream/master'