Add standard Xcode gitignore file.
Update Xcode project to latest version.
Fix font withSize/withAttributes warnings, update font size to 14 and clean up code.
Update README contents and use Markdown format.
Update class comments.
Convert to Objective-C ARC.

Not completed though as we get a warning about the window variable in
the app delegate. I believe this was an old way of doing things so
might have to make some project changes as the window has a XIB file
(MainWindow).