Reel adapter fixups

This is a snapshot of the Reel adapter I'm using in the Cryptosphere.

It includes some general refactoring and the following notable changes:

* Support for mapping extended HTTP verbs to the _method pseudoparameter (e.g.
  for WebDAV support)
* Joins to the foreground actor rather than sleeping the thread. This fixes
  deadlock detection issues
* Streaming support: passes Reel's request.body objects through unmolested
  rather than using LazyRequestBody