Adjust X axis in CDF plot

[pcarbo]

@willwerscheid One issue I noticed with the plots is that the X axis is not adjusted for scale. For example, this is a plot I created for a normal prior with a large sd:

plot(g,incl_pm = FALSE,incl_cdf = TRUE)

As you can see it would be helpful if the X axis could be adjusted somehow.

[pcarbo]

Relatedly, I noticed that the Y axis sometimes doesn't start at 0. The Y axis should always be between 0 and 1, I think?

[willwerscheid]

By default the x-axis limits are chosen to span the range of the data. I agree about the y-axis and I also agree that we should have a xlim parameter in plot.ebnm.