Added code to compare with Sequential Fib version.

+ Added some notes about things left to do.
+ Added getFib and getRecursiveFib methods in Fib for easy comparison
  between sequential and parallel code.
+ Added empty loop in both versions to see if it led to a speedup in the parallel version.
Finally got some real speedup (after adding a busy loop).

I've made tryWaitForReadyNode use a Condition variable but it doesn't
seem to have made much difference.