bugfix: convert ints to strings before write

Ensures all scalar values (like ints) are converted to string types before write.
Add unittests for #829
Add changelog entry for #829
Merge branch 'tgolly-patch-1' into develop

* tgolly-patch-1:
  Add changelog entry for #829
  Add unittests for #829
  bugfix: convert ints to strings before write