Use Polymer Analyzer for finding documents

[justinfagnani]

First, this project is awesome! :)

Second, you should be able to save a lot of code if you use the Polymer Analyzer to load all the files in a project. It walks all imports, and has a convenient analyzePackage() method that tries to give a nice default for what files are in a package. Also it will support more import methods than just HTML Imports. It's growing support for our Lazy HTML Imports behavior, and for ES modules. As the Analyzer improves over time, you'll get the advantage of it.