Add file parsing for .js and .hbs files.

[rwjblue]

• Create a model for JavascriptContent
  • Add ability to get the list of imports, and their corresponding FileInfo's (from the FileInfoCollection).
  • Figure out how to update import paths (keeping relative or absolute versions)
• Create a model for TemplateContent Implement template renderable invocation detection. #22
  • Add ability to get list of component and helper invocations Implement template renderable invocation detection. #22
  • Figure out how/if they need to change when the files are moved (likely only an issue for {{foo/bar}} type invocations).
  • Determine if a given component/helper is only used from within a single location and make it a local private component.