fixed a bug in merge-3-4
Split files for ch3, moving on to binomial heaps with exercises from leftist heaps incomplete.
Finished Ch 3.1 Leftist Heaps exercises 3.3 and 3.4.

The trick was to accept no benefits or clarity would be achieved from
completing this particular exercise, but instead a path/template is created from
which benefits in lazy/concurrent environments (exercise 3.4) are
obvious.

I have not tested the solution to the exercise, but it seems to make
sense. Moving on.