Update NEWS

Author: mayer79

NEWS.md

@@ -2,11 +2,15 @@
 
 ## Performance improvements
 
-- Significant speed-up for data objects with *single class "data.frame"*, i.e., no data.tables or tibbles or grouped data etc. This change makes it almost as fast to work with data.frames as with matrices.
-- Slight speed-up for single-output predictions.
-- Slight speed-up for factor-valued predictions.
+- Significant speed-up for pure data.frames, i.e., no data.tables or tibbles.
+- Some small performance improvements, e.g., for factor predictions and univariate predictions.
 - Slight speed-up of `permshap()` by caching calculations for the two special permutations of all 0 and all 1. Consequently, the `m_exact` component in the output is reduced by 2.
 
+## Documentation
+
+- Rewrote many examples in the README.
+- Added reference to Erik Strumbelj and Ivan Kononeko (2014).
+
 # kernelshap 0.4.0
 
 ## Major changes