v0.4.0

Changelog

ca78178 Add missing makefile
f384737 Enrich version information. Fixes #15
a37723c Add CoC and contributing docs
3344092 Add external configuration. Fixes #14
bee268c Add license headers. Fixes #13
2e9b6e2 Fix auto detection of gradle/maven. Fixes #11
f1e0fc7 Support additional goal/task mappings. Fixes #10