Tweaks doc style and js

# Tweaks doc style and js
Hi. I did tweak the following two feature to doc.
+ Every time I need a head line's link, I made a hash link by myself. But, I noticed today that there is a toc menu. So I would like to stand out a little bit more this.
+ When I debugging doc, sometimes toc menu had may not be rendered due to the timing of the DOM loaded.

## Compare preview
+ Current: https://www.npmjs.org/doc/cli/npm.html
+ My fixed: http://watilde.github.io/npm/html/doc/api/npm.html

### Notes
Since this problem might be a matter of preference, please close it if unnecessary likely.

Thanks!