0.4.3

• refactoring of qth_survival_times: it can now accept an iterable (or a scalar still) of probabilities in the q argument, and will return a DataFrame with these as columns. If len(q)==1 and a single survival function is given, will return a scalar, not a DataFrame. Also some good speed improvements.
• KaplanMeierFitter and NelsonAalenFitter now have a _label property that is passed in during the fit.
• KaplanMeierFitter/NelsonAalenFitter's inital alpha value is overwritten if a new alpha value is passed
  in during the fit.
• New method for KaplanMeierFitter: conditional_time_to. This returns a DataFrame of the estimate:
  med(S(t | T>s)) - s, human readable: the estimated time left of living, given an individual is aged s.
• Adds option include_likelihood to CoxPHFitter fit method to save the final log-likelihood value.