Changes to support iPad

Switch to require a UINavigationController. Get rid of present view
controller calls and use push / pop view controller calls. Require the
caller to dismiss the view controller in case of DONE or CANCEL.
Update readme
Set popover content size and allow all orientations if iPad
Bug fix
More iPad enhancements
Fix readme typo
Another readme update since cancel is required
Merge pull request #9 from jjxtra/master

Enhancments for iPad