Changed to use NUnit.
Need not to have an abstract class now.
Put new instances creation of concrete observers and subject in SetUp attribute.
Renamed getInstance to be newInstance.
Removed duplications of attaching cities and setting time.
Removed unused method.
Renamed getInstance with newInstance.
changed observer.syncTimeServer to observer.syncWithTimeServer.
Removed the abstract subject.
Change the public time member variable to be protected.
Changed DST to be a static class.
Merge pull request #1 from bjdp/master

ok