Another level set translation article

	new file:   visualization/_posts/2013-12-25-the-level-set-method-lecture-notes.md
	new file:   visualization/img/levelset2/boundary-formulation.png
	new file:   visualization/img/levelset2/discretized-distance-function.png
	new file:   visualization/img/levelset2/evolving-interface.png
	new file:   visualization/img/levelset2/explicit-problems.png