add examples

example of matplotlib figure
Minor fix
Support --ncolor option
Improve performance
Seek input file position to 0 if possible
More performance tuning
Add c module generated by cython
Update Makefile
Update setup script for building c module
Do cell size detection only if needed
Add logging
Use c implementation if possible
Bump version
Add c implementation file generated by cython
Update changelog
Update README
Minor fix
Drop Python 2.5
Use Pillow insted of PIL
Enable 256 color by default