resolves #1203 provide access to output file & dir through document object

- pass raw (expanded) target directory to Asciidoctor#load as :to_dir option
- expose options on document as frozen Hash
- set outfile and outdir attributes before converting unless safe mode >= server
Merge pull request #1217 from mojavelinux/issue-1203

resolves #1203 provide access to output file & dir through document object