enable css overriding

Should you wish to incorporate.  It's a very basic solution (i.e., a little kludgy) but it works.  I'm using it at the moment to simply override the anchor tag coloring for links.  As is, they're invisible until you happen to hover over one.

Here's an example of how I'm calling doc-n-toc now for hummingbird.js
`doc-n-toc docs/intro.md docs/examples.md docs/contribute.md --css docs/my.less --title "Hummingbird v<%= pkg.version %>" > index.html`