performance 0.10.2

General

• Revised usage of insight::get_data() to meet forthcoming changes in the
  insight package.

Changes to functions

• check_collinearity() now accepts NULL for the ci argument.

Bug fixes

• Fixed issue in item_difficulty() with detecting the maximum values of an
  item set. Furthermore, item_difficulty() gets a maximum_value argument
  in case no item contains the maximum value due to missings.