Given a N by M matrix of numbers, print out the matrix in a spiral.
For example, given the following matrix:
[[1, 2, 3, 4, 5],
[6, 7, 8, 9, 10],
[11, 12, 13, 14, 15],
[16, 17, 18, 19, 20]]
You should print out the following:
1
2
3
4
5
10
9
8
7
6
11
12
13
14
15
20
19
18
17
16