rumrunner 0.2.0

Rumfile is a Rake-based utility for building projects using multi-stage Dockerfiles. Rumfile allows users to minimally annotate builds using a Rake-like DSL and execute them with a rake-like CLI. Carfofile has the following features: * Rumfiles are completely defined in standard Ruby syntax, like Rakefiles. * Users can specify Docker build stages with prerequisites. * Artifacts can be exported from stages * Stages' build steps can be customized * Shell tasks are automatically provided for every stage