A few improvements

1. changed the file order for TableCell
1. made a few adjustments to the TableCell
  1. cell is loaded from nib with a single method (this improves reusing the cell later)
  1. cell is configured with a single line of code instead of a bunch of lines everytime
1. improved the navigation method to push the center controller (DRY)
1. made the row count in LeftViewController a bit more dynamic
1. viewcontroller are now loaded from nib with a single unified line instead of `initWithNibName:bundle:` this is for your own safety to ensure you load the correct nib file