Christian M. says it's bad to chain one constructor call from another.

Christian M. says it's bad to chain one constructor call from another.
I can't find anything that addresses this in Stroustrup, but I also don't
see them doing this in any of their examples.  So I have rewritten this
instance to use default arguments to accomplish the same thing.  I imagine
there are other instances of this same sort of thing in other classes to
be fixed at a later date.