Bug fix

Fixed the following but (was due to overwriting of name df1 in function
body of tne.survfit, also was needed add handler in subAgg for one each
timepoint being unique.

set.seed(5)
time<-rexp(20)
event<-rep(c(0,1),10)
c<-c(rep(1,10), rep(2,10))

df1<-data.frame(time, event, c=c)

s10<-survfit(Surv(time, event)~c, data=df1)

tne(s10) #works
tne(s10, asList=TRUE) #doesn't work

comp(s10)