You can actually go through different approaches.
My favorite one this far (basically because it’s more complete) is to use the API Portal for publishing.
When doing it, you can manage it as a content manager (put your own sections/pages), but it will automatically place a CONSOLE section that will display the documentation you are trying to achieve.
Another nice project I’ve checked last week is:
The major advantage of this one, is that with just calling a command you can generate the HTML (very standalone).
The cons are basically it’s not finished, so, you cannot take advantage of all RAML features.
Give both a try and let me know what do you think!