message if no sector or no track is created
fixed the bug when text facing is 'bending'
link does not reply on track.index
add track.index = 0 in circlize function
set default transparency to 0.5
rendered by knitr
add clock.wise argument to draw.sector
highlight.chromosome can draw more than one chromosome
use knitr to render vignettes
ring with filled color
vignettes are now rendered by knitr