When requesting :all_pages, result has metadata of the first response.

Example:

```clojure
user> (require '[tentacles.events :as events])
nil

user> (def es (events/events {:all_pages true}))
#'user/es

user> (meta es)
{:links {:next "https://api.github.com/events?page=2"},
 :api-meta
 {:etag "...",
  :last-modified "...",
  :call-limit 60,
  :call-remaining 58,
  :poll-interval 60}}
```

(The slight inefficiency of calling with-meta with each call to lazy-cat — then not using most metadata — should be insignificant.)