Coerce non-semver into semver (#34)

.github/workflows/test.yml

@@ -98,6 +98,10 @@ jobs:
             otp-version: '23'
             rebar3-version: '3.14'
             os: 'ubuntu-20.04'
+          - elixir-version: 'v1.12'
+            otp-version: '24'
+            rebar3-version: '3.15'
+            os: 'ubuntu-20.04'
     steps:
       - uses: actions/checkout@v2
       - name: Use erlef/setup-beam