Issue #3445744 by Andriy Khomych: Updates README.md about merging module dependencies.

README.md

@@ -112,7 +112,8 @@ lines describe all operations and some terminology.
   one'), which prevents the replacing of old parents.
 
 - Merging
-  To use it enable the taxonomy_manager_merge submodule.
+  To use it add term_merge, term_reference_change modules and
+  enable the taxonomy_manager_merge submodule.
   With the merging action, you can put terms with the same meaning together
   (e.g. your vocabulary contains: SoC, Summer of Code, GSoC, Google Summer of
   Code). All terms, that get merged into one other, get synonyms of resulting