Fix ordering of tasks

[mortenlj]

Correct the execution order of deep dependency trees. Fixes #28.

[mortenlj]

Strangely enough, this fixes the example files I created for #28, but it doesn't fix the problem in the Bakefile where I first encountered the problem.

I will see if I can revisit this tomorrow and see if I can figure out why it is still failing on my real project (and try to extend the test-case to catch it).

[mortenlj]

I will see if I can revisit this tomorrow and see if I can figure out why it is still failing on my real project (and try to extend the test-case to catch it).

This seems to have been me running the old version by mistake, it works now. This rather simple change seems to fix the ordering for me.