doc: revisit changelog for upcoming 0.9.0

* Marked all changelog entries either with an issue ID or with a pull
  request ID.
* Added a changelog entry for #144 (ignoring of an error in
  `crud.pairs()`).
* Marked testing changes explicitly, move them down in the list.

Author: Totktonada

CHANGELOG.md

@@ -9,24 +9,25 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Changed
 
-* Names of errors generated by CRUD operations have been unified.
+* Names of errors generated by CRUD operations have been unified (PR #184).
 * Opmimize `crud.select()` / `crud.pairs()` for one replicaset case (say, when
   `bucket_id` is passed or deducible from conditions). It gives 13% boost on
-  the case from #220.
+  the case from #220 (PR #226).
 
 ### Fixed
 
-* Damaging of opts table by CRUD methods.
+* Ignoring of an error in `crud.pairs()` (#144).
+* Damaging of opts table by CRUD methods (#192).
 * Ignoring of `bucket_id` option in `crud.select()`/`crud.pairs()` (#220).
 
 ### Added
 
-* Added integration with service coveralls.io.
-* Added integration with luacov that allows to generate report with code
-  coverage statistics.
 * `crud.len()` function to calculate the number of tuples
   in the space for memtx engine and calculate the maximum
   approximate number of tuples in the space for vinyl engine.
+* Testing: added integration with service coveralls.io (PR #195).
+* Testing: added integration with luacov that allows to generate report with
+  code coverage statistics (PR #195).
 
 ## [0.8.0] - 02-07-21