Version bump

Version 1.6.0

Release v1.5.0

Removes test helper (fails in CI). Upgrade notes.

Releasing merit 1.3.1

Releasing version 1.3.0. Fixes merit-gem#47

Bug fix. Releasing 1.2.3. Fixes merit-gem#39

Checking if const exists during installation. Release 1.2.2. Fixes me…

…rit-gem#39

Releasing version 1.2.1.

Releasing merit 1.2.0