review feedback from PR #183

* `sourceRoot` is a decorative value passed thru container, writer and recast to facilitate grouping output files from a container into a common folder when debugging. It defaults to `/` as a way to avoid the path to the current page affects the representation of the static transpilation process (this is still up for discussion).
* `basePath` is an internal value to compute the relative path with respect to the container, the computed value will be used as `sourceFileName` when outputting a transpiled file. It defaults to `process.cwd()`