Add --clever-links and --monospace-links options

[zanerock]

Jsdoc defines options for 'clever links' which render non-URL links (e.g., links to functions, classes, modules, etc.) in monospace font, and also 'monospace links', which renders {@link}s in monospace by default.

The clever links and monospace links features would actually be implemented in the 'dmd' project, proposed here dmd#85.

[75lb]

PRs squash-merged into master - this will be in the next version.. in the meantime, give everything a nice test please in the pre-release.

npm install jsdoc-to-markdown@next