Khan/khan-exercises — pull request #33651 by cuhlik (2012-11-14 04:30:11+00:00)
Title: I added a few more problem types to permutation_1.  This is my first attempt to contribute to Khan Exercises, so feel free to be brutally honest and complete with any criticism or advice.

Added 3 more problem types:
stacking colored blocks,
rearranging digits in a number, and
travelling salesman sequencing.
Equalized data-weights so all 5 problem types are
selected with equal probability.