GUI should make apparent unsaved changes
When you modify a document in most applications, on Mac, the red close button changes to have a dot in its center, denoting there are unsaved changes. On other OSes, what's commonly done is to put an asterisk before the filename in the title bar. Kepler doesn't do this.
For the mac, this can almost be solved by just modifying TableauFrame.setModified to include:
JRootPane root = this.getRootPane();
root.putClientProperty( "Window.documentModified", Boolean.TRUE);
root.putClientProperty( "Window.documentModified", Boolean.FALSE);
However we should also watch for undos, and undo the dot or asterisk as appropriate.