http_spew 0.6.0 - even less

Rack "to_path" support is dropped since few servers can
take advantage of this in a non-buggy way.

As a consolation, #each should be less GC-intensive by
with explicit calls to String#clear to reduce memory
pressure.

3 changes since 0.5.0

      pkg.mk: avoid network for "gem install"
      request: drop to_path support
      explicitly clear large buf when it is obviously safe