Allow attributes to be defined via URL parameters
Allow attributes to be defined via URL parameters

Resolves #99

bbucko/asciidoctor-chrome-extension,asciidoctor/asciidoctor-chrome-extension,rotty3000/asciidoctor-chrome-extension,Mogztter/asciidoctor-chrome-extension,rotty3000/asciidoctor-chrome-extension,asciidoctor/asciidoctor-chrome-extension,asciidoctor/asciidoctor-chrome-extension,rotty3000/asciidoctor-chrome-extension,Mogztter/asciidoctor-chrome-extension,bbucko/asciidoctor-chrome-extension,bbucko/asciidoctor-chrome-extension