insight 1.0.2

Changes

• get_datagrid() gives a more informative error message when a variable
  specified in by was not found in the data.

• The by argument in get_datagrid() gets a new token-option, "[sample <number>]",
  to draw a random sample of values.

Bug fixes

• Option "terciles" and "terciles2" in get_datagrid() were swapped, i.e.
  "terciles" was doing what was documented for "terciles2" and vice versa.
  This has been fixed.

• include_random in get_datagrid() now works for nested random effects, i.e.
  for more than one group level factor in the random effects.

• Fixed issue in get_varcov() for models of class brmsfit that included
  monotonic effects.