Improved docstrings in lib/_augment.pyx (#2062)

* added missing CHANGELOG entry for PR #2048

* ensured `lib.distances.distance_array()` always returns an array

package/CHANGELOG

@@ -80,7 +80,8 @@ Enhancements
   * Added dihedrals.py with Dihedral, Ramachandran, and Janin classes to
     analysis module (PR #1997, PR #2033)
   * Added the analysis.data module for reference data used in analysis (PR #2033)
-  * Added dihedrals.py with Ramachandran class to analysis module
+  * Most functions in `MDanalysis.lib.distances` previously only accepting
+    arrays of coordinates now also accept single coordinates as input (PR #2048)
   * Performance improvements to make_whole (PR #1965)
   * Performance improvements to fragment finding (PR #2028)
 
@@ -120,6 +121,9 @@ Changes
     (Issue #1894)
   * removed unused function MDAnalysis.lb.mdamath.one_to_many_pointers()
     (issue #2010)
+  * Box input for functions in `MDAnalysis.lib.distances` is now consistently
+    enforced to be of the form ``[lx, ly, lz, alpha, beta, gamma]`` as required
+    by the docs (Issue #2046, PR #2048)
   * Added periodic keyword to select_atoms (#759)
 
 Deprecations