--------------------------
Sort numbers in a "snake"
--------------------------
Write a functions that takes a matrix and sorts the entries in descending order and places them in a "snake" pattern in a matrix of the same size as the original matrix. The snake starts from the upper left corner and goes down, right, up, right, down, and so on.

Syntax: B = snakesort(A)

where 	A is the original matrix,
	B is the sorted matrix.

Examples:

>> A = [8 4 5;
	7 3 1;
	2 6 9];

>> B = snakesort(A)

B =

   9  4  3
   8  5  2
   7  6  1

>> A = [10 11 12 13;
	6  7  8  9];

>> B = snakesort(A)

B =

   13  10  9  6
   12  11  8  7

--------------------------