Update the changelog.

Fix #701

CHANGELOG.md

@@ -4,9 +4,30 @@ documented here.
 
 This project adheres to [Semantic Versioning](https://semver.org/).
 
-## [0.19.0] - WIP
+## [0.20.0]
+### Added
+  * `cholesky.rank_one_update(...)` which performs a rank-one update on the cholesky decomposition of a matrix.
+  * `From<&Matrix>` is now implemented for matrix slices.
+  * `.try_set_magnitude(...)` which sets the magnitude of a vector, while keeping its direction.
+  * Implementetanions of `From` and `Into` for the conversion between matrix slices and standard (`&[N]` `&mut [N]`) slices.
+  
+### Modified
+  * We started some major changes in order to allow non-Copy types to be used as scalar types inside of matrices/vectors.
+
+## [0.19.0]
 ### Added
   * `.remove_rows_at` and `remove_columns_at` which removes a set of rows or columns (specified by indices) from a matrix.
+  * Several formatting traits have been implemented for all matrices/vectors: `LowerExp`, `UpperExp`, `Octal`, `LowerHex`,
+  `UpperHex`, `Binary`, `Pointer`.
+  * `UnitQuaternion::quaternions_mean(...)` which computes the mean rotation of a set of unit quaternions. This implements
+  the algorithm from _Oshman, Yaakov, and Avishy Carmi, "Attitude estimation from vector observations using a genetic-algorithm-embedded quaternion particle filter."
+
+### Modified
+  * It is now possible to get the `min/max` element of unsigned integer matrices.
+
+### Added to nalgebra-glm
+  * Some infinite and reversed perspectives: `::infinite_perspective_rh_no`, `::infinite_perspective_rh_zo`,
+  `::reversed_perspective_rh_zo`, and `::reversed_infinite_perspective_rh_zo`.
 
 ## [0.18.0]
 This release adds full complex number support to nalgebra. This includes all common vector/matrix operations as well