Support for Response Builder.

[ShaileshSurya]

Rough Design:

func apiResponse(w http.ResponseWriter, r *http.Request) { 
  w.WriteHeader(http.StatusOK)
  w.Header().Set("Content-Type", "application/json")
  w.Write([]byte(`{"message":"hello world!"}`))
}

hammer.ResponseBuilder(http.ResponseWriter)
.WithStatus(http.StatusOK).
WithHeader("content-type","application/json").
WithBody(&map or &struct).
send()

The design is too vague but needs more investigation.

[ShaileshSurya]

@ZachPlunkett would you like to have a look at this as well.