Pass '...' through to chart.TimeSeries() functions (#183)

* Pass '...' through to chart.TimeSeries.builtin()

This allows users to provide arguments to plot.xts() that aren't
explicit arguments to the chart.TimeSeries() functions.

For example, it allows users to remove the dates from the top right of
the plot:

   set.seed(21)
   returns <- xts(rnorm(100, 0, 0.005), .Date(1:100))
   chart.CumReturns(returns, main.timespan = FALSE)

This doesn't work with the current code.

* Add '...' to docs

Should have been included in previous commit.

R/chart.TimeSeries.base.R

@@ -81,7 +81,8 @@ chart.TimeSeries.base <-
                                       grid.color=grid.color, 
                                       grid.lty=grid.lty, 
                                       xaxis.labels=xaxis.labels,
-                                      yaxis.pct=yaxis.pct)
+                                      yaxis.pct=yaxis.pct,
+                                      ...)
              return(p)
            },
            ggplot2 = {

R/chart.TimeSeries.builtin.R

@@ -37,7 +37,8 @@ chart.TimeSeries.builtin <-
            grid.color, 
            grid.lty, 
            xaxis.labels,
-           yaxis.pct){
+           yaxis.pct,
+           ...){
 
     y = checkData(R,method='xts')
 
@@ -100,7 +101,8 @@ chart.TimeSeries.builtin <-
                   yaxis.left = yaxis.left, 
                   yaxis.right = yaxis.right, 
                   grid.col = grid.color, 
-                  legend.loc = NULL)
+                  legend.loc = NULL,
+                  ...)
 
     if(!is.null(event.lines)) {