text: Title: Add smooth survival plot to either kdeplot or ecdfplot
  Body: In Seaborn, if someone wants to plot a _smooth_ [survival function](https://en.wikipedia.org/wiki/Survival_function) (defined as 1-the CDF), there are two suboptimal solutions:
  
  - seaborn.kdeplot can plot a smooth CDF plot
  - seaborn.ecdfplot can plot a _non-smooth_ 1 - empirical CDF
  
  But if I want a KDE-estimated smooth plot of 1-CDF, I can't find a good solution.