Added functionality to simulations.realize_lcs to simulate light curve
data at a subset of observation points among those in an observation
table, where the selection is based on a time window around peak. The
time window can be defined by the user, and is convenient to define such that
all SN are within a particular window of phase for all SN, irrespective
of redshift.
- The feature is used by default with a phase window of (-30, 60) days
- The value can be changed by setting the argument phaseWin=[tmin, tmax]
  of the simulations.realize_lcs function.
- The feature can be turned off by setting the argument phaseWin=None