Swig adapter

I wrote an adapter for the [Swig](http://paularmstrong.github.io/swig/) template engine.  

The most important aspect of dev to note is referenced in [docs/swig.md]:(https://github.com/carrot/accord/blob/swig/docs/swig.md)

> There is no way to set a "base path" in Swig's `render` or `compile` methods, which means external file requests (see: [template inheritance](http://paularmstrong.github.io/swig/docs/#inheritance)) Swig's `renderFile` and `compileFile` methods both parse the file path through the first argument passed.  Thus, the Swig adapter overwrites the `Adapter` class's `renderFile` and `compileFile` methods.

Otherwise, Swig was :cake: to work with.