Add bin/ansi2html for converting ansi from stdin to html

I tried to follow your style conventions. If you accept this PR, could you also bump up the npm version (e.g. `npm version patch`, `git push `, `npm publish`? I think the repo link on npm is outdated..

Here is a usage example, btw: `git log --color  | ansi2html | marked > diff.html`

I'm using marked to convert the paragraphs to html.