Use tstmleSI to handle continuous outcome

[wxwx1993]

Dear @imalenica,

I implemented the tstmleSI function, yet found the function can only allow a binary outcome variable. I think this is due to the outcome_type being hard-coding to be "binomial" in both initEst and fluctuate functions.

Whether a code change to allow continuous outcomes is possible?

[imalenica]

Thanks for pointing it out. I'll update the code in the next few days.