preprocessor doesn't works when installed into a place that differ from yuidocjs

[okuryu]

Currently, preprocessor seems to works only when installed in the same place with yuidocjs. This means preprocessor works in one of two conditions as follows.

$ npm install -g yuidocjs
$ npm install -g yuidocjs-die-on-warnings

or

$ npm install yuidocjs
$ npm install yuidocjs-die-on-warnings

I think that it has the space to enhances the preprocessor feature for this problem because it could a situation like installed them in separate places.