icdfPlot in updateCmap of EqualSpaceCdfUpdate doesn't returns infinity at 0 and 1.

[xxxnell]

Theoretically, inverse-cdf (quantile) returns ±∞ at 0 and 1. However, due to the limitations of the way Sketch treats boundaries, this value only returns a finite large value.

For now, we take the approach of artificially removing the two values of the boundaries, but we need a more sophisticated way of getting a new Cmap in this function.