simpler while loop, add source_lines method to Document
resolves #103 include document title when header/footer disabled

- unset the notitle attribute to enable <h1> at top of embedded output
resolves #163 support :doctype and :backend keys in options hash

- also add test to ensure that doctitle can be set using :doctitle: attribute
Merge pull request #177 from mojavelinux/minor-cleanups

simpler while loop, add source_lines method to Document
Merge pull request #178 from mojavelinux/title-for-embedded

Resolves #103 include document title when header/footer disabled
Merge pull request #179 from mojavelinux/doctype-backend-options

resolves #163 support :doctype and :backend keys in options hash
organize code in Asciidoctor module; optimize block match

- put all code inside an Asciidoctor module block
- move debug operations into Debug submodule
- optimize block matching by using a single regexp
- add support for fenced code blocks