updated get_tmin_tmax
updated get_tmin_tmax

Update of the get_tmin_tmax method:
- added a use_stresses keyword to obtain tmin/tmax from the stresses
- pastas now supports simulation outside calibration period and even extrapolates outside provided time series ranges (e.g. supports forecasting)
- Simulation did not take warmup period into account, sometimes leading to strange results and lower scores of fit statistics

pastas/pasta,gwtsa/gwtsa,pastas/pastas