Fixed internal array indexing to row-major
Fixed internal array indexing to row-major

Now we can just iterate over a Grid object in row-major order (ie: 0,0
1,0 2,0 0,1 1,1 2,1 ...) which follows the principle of least surprise
when creating a Grid object using the from_array static method.

agentultra/Horton,agentultra/Horton