resolves #14 and resolves #12
resolves #14 and resolves #12

- specify project directory when invoking Gradle
- emit usage on failure and when -h is passed
- fail sooner

azuwis/asciidoctor-fopdf,asciidoctor/asciidoctor-fopub,asciidoctor/asciidoctor-fopub,getreu/asciidoctor-fopub,azuwis/asciidoctor-fopdf,getreu/asciidoctor-fopub,asciidoctor/asciidoctor-fopub,getreu/asciidoctor-fopub