Only set a `context` reference on "legacy" root-level views
 (that is, views that do not declare a `wiring` mapping and therefore do not support the new dependency injection API).  This means that newer components that use DI cannot manually muck with the context object since they won't have a handle to it.  A future version of Geppetto will remove this conditional setting of the Context in favor of using DI.  Closes #36