Preprocessor support for inlining scripts and stylesheets. This converts
the inlining process into an asynchronous waterfall to be interface
compatible with existing processing libraries, in particular
[less](https://github.com/wballard/vulcanize-less) and
[browserify](https://github.com/wballard/vulcanize-browserify].

With this tweak, vulcanize is all the build tool needed to create stand
alone elements from mixed language sources.