draw_letters_on_canvas simplified a bit, also now it takes matrix of heights, not ppm
refactor to a more functional style
matrix returned by #get_logo and used by #draw_letters_on_canvas is now plain matrix,not a hash
exract logo canvas into separate class
make it possible to draw sequences and snp-sequences
extract drawing a position into it's own method
rewrite snp drawing so that order of nucleotides depends on input
extract LogoCanvas into its own file