Add a simple option parser for comma-delimited lists, and add more features to Remarkup code blocks

Summary:

• Add a parser for lang=php, lines=10, name=example.conf type stuff.
• Add those features to code blocks.

Test Plan:

• Unit tests.
• Made code blocks with the new features in Phabricator.

Reviewers: davidreuss, btrahan, jungejason

Reviewed By: btrahan

CC: aran

Maniphest Tasks: T336

Differential Revision: https://secure.phabricator.com/D1416