Subversion Demo #2 error fixed

There was an error in the Subversion Demo #2 section of the notes.  I forgot to include a "svn add" command.  If you followed it and were wondering why Hello.java did not get committed to the repository when you typed "svn commit", that's why.  Subversion did not know it was supposed to be tracking Hello.java and needed to be told to.  The notes have been updated.