Add option to generate torus grids
Planted Ordering principle: an element is allowed not to have predecessors.
Improve Tseitin generator from O(VE) to O(E)
Merge pull request #13 from marcvinyals/torus

Add option to generate torus grids
Merge pull request #14 from marcvinyals/profile

Improve Tseitin generator from O(VE) to O(E)