Sort headers in YAML output

go/fake-http/README.md

## TODO
- replay from log instantly (i.e. operate like a request cache)
    - ensure every request is cached max once?  at least in the response
      defn?
    - make it possible to download the cache
        - /_cache, analogous to /_log?
        - or reuse /_log, which wouldn't need new code, but would make
          it impossible to download the log.  damn...
            - how about /_log?cache=true?
            - or make /_log redirect to /_cache if `-cache` is enabled
- /_clear endpoint
- some kind of templating (request info + random functions?)
- lua integration? ;)

go/fake-http/fake-http.go

	"os"
	"os/exec"
	"path"
	"sort"
	"strings"
	"time"
	responseBody *bytes.Buffer
}
type byHeaderName []Header
func (hs byHeaderName) Len() int           { return len(hs) }
func (hs byHeaderName) Swap(i, j int)      { hs[i], hs[j] = hs[j], hs[i] }
func (hs byHeaderName) Less(i, j int) bool { return hs[i].Name < hs[j].Name }
// AsResponse returns a Response representation of the entry.
func (e LogEntry) AsResponse() Response {
	headers := make([]Header, 0, len(e.response.Header))
			headers = append(headers, Header{Name: name, Value: val})
		}
	}
	sort.Sort(byHeaderName(headers))
	return Response{
		Method:  e.request.Method,
		Path:    e.request.URL.Path,