v0.6.1

Breaking changes:

• Changed interface of BaseApplication to use Request and DispatchInfo (see
  below). This breaks downstream clients of this codebase.

Other notable changes:

• Added new application SimpleResponse, which is kind of like a one-file
  StaticFiles.
• Introduced a Request class specific to this project, instead of just
  "absorbing" Express's Request and Response objects. Our Request holds
  both the underlying request and response (and other related goodies). For now,
  the underlying Express bits are exposed to clients, but the intention is for
  them to get hidden and for this project's API to be sufficient.
• Relatedly, introduced new class DispatchInfo, to hold information about a
  request dispatch-in-progress (i.e., routing information, more or less). In
  Express, the equivalent state is represented by mutating the request object,
  but we're an immutable-forward shop here.
• Got rid of direct uses of Express's Request and Response classes, other
  than within our Request. Most notably, the request logging code got a
  major rewrite.
• Reworked most of the code in our Request class that does
  actually-Express-specific stuff, to instead do approximately what Express
  does, or just not do it at all. Notably, we no longer try to deal with reverse
  proxies; support will probably be added for them eventually (assuming demand).
• Reworked StaticFiles to use our Request instead of wrapping
  express.static().