handle color vector recycling

- We need to be aware of the length of the color vector that is
  passed in the case of type="h". If the length of the vector is
  less than the number of elements in x, then R will recycle the
  colors. This is not the behavior we want.
- To fix this, I added a simple check of the length of the color
  vector and number of observations of x. If the color vector has
  fewer elements than the number of observations, then we only use
  the first element from the color vector.

see #224

R/plot.R

@@ -97,6 +97,8 @@ chart.lines <- function(x,
            } else {
              colors <- if (is.null(col)) 1 else col
            }
+           if (length(colors) < nrow(x[,1]))
+               colors <- colors[1]
            lines(xx$Env$xycoords$x,x[,1],lwd=2,col=colors,lend=lend,lty=1,type="h",...)
          },
          p=, l=, b=, c=, o=, s=, S=, n={