Full nodejs support

Requires review and if accepted will null the need of the `nodejs` branch. There is a ton of small build refactorings in here so this diff is going to be difficult to process -- I recommend viewing the actual branch: https://github.com/megawac/roslibjs/tree/umd-modules

I'm still in the process of running the examples and integration....

Fixes #53

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Additional install steps:

- Install `cario`. System specific guide: https://github.com/Automattic/node-canvas/wiki/_pages

```sh
$ [sudo] apt-get install libcairo2-dev libjpeg8-dev libpango1.0-dev libgif-dev build-essential g++
```