R/plot.R: modified the binMatrix function that did not have the expected behavior

Signed-off-by: Charles Joly Beauparlant <Charles.Joly-Beauparlant@crchul.ulaval.ca>
rename vignettes/MetaMineR.Rmd to vignettes/metagene.Rmd

Signed-off-by: Charles Joly Beauparlant <Charles.Joly-Beauparlant@crchul.ulaval.ca>