Convert a text representation of a Sudoku to tikz.

I wrote this program because I couldn't find how to change the color of a cell
using in the Latex Sudoku package
(http://www.ctan.org/tex-archive/macros/latex/contrib/sudoku/).

The program understand both the Latex Sudoku package format, and the Polyform
Puzzler (http://puzzler.sourceforge.net/) format.

A cell with an 's' as a suffix is interpreted as a solution and printed in red.

By the default, the output of the program is a tikz file. With the -p option,
it also produce a PDF file. The -f option add the string 'Start position in
black, solution in red' as a footnote.


Examples:

$./sudoku2tikz.py *.sud 
                  
                  Convert all the *.sud files to tikz.

$./sudoku2tikz.py -f -p *.sud 
                  
                  Convert all the *.sud files to tikz, including the
                  footnote. It a PDF file for each Sudoku file.

WARNING: The program assume that all the dependencies (Python, Latex, Tikz) are
met. Otherwise it will fail miserably. Also, no effort is made to check that
the format of the Sudoku description is correct.

The following are examples of valid Sudokus descriptions:

9 . . 4 . . . 1 6
2 . . . 5 6 7 . .
. . . 8 7 1 4 . 2
6 3 . . 1 . . 5 .
. . . . 8 . . . . 
. 7 . . 3 . . 4 9 
7 . 6 2 4 8 . . .
. . 8 3 9 . . . 4 
3 9 . . . 7 . . 5

1 6s 2s 8s 5s 7 4s 9 3s
5s 3 4s 1s 2 9s 6s 7s 8
7s 8s 9 6 4s 3s 5 2s 1s
4s 7s 5 3 1s 2s 9 8s 6s
9s 1 3s 5s 8 6s 7s 4s 2
6 2s 8s 7s 9s 4 1s 3s 5s
3 5s 6s 4s 7s 8s 2s 1 9s
2s 4 1s 9s 3s 5s 8s 6s 7
8s 9s 7 2s 6s 1s 3 5s 4s

|5|3| | |7| | | | |.
|6| | |1|9|5| | | |.
| |9|8| | | | |6| |.
|8| | | |6| | | |3|.
|4| | |8| |3| | |1|.
|7| | | |2| | | |6|.
| |6| | | | |2|8| |.
| | | |4|1|9| | |5|.
| | | | |8| | |7|9|.

Contact: alejandro.weinstein@gmail.com