Went from ~70% to ~96% test coverage.
Minor features:
- Proper HEAD support
- Support more of net/http's interfaces: Hijacker, CloseNotifier, Flusher
- Pluggable loggers for the LoggerMiddlware and the PanicNotifier.
NOTE: Some types had their exportedness changed to private, so this release does have some minor backwards incompatibility if you happened to be using those types (there was no reason to).