Add compatibility for RSpec 2.99
Add compatibility for RSpec 2.99

RSpec 2.99 adds a deprecation formatter which uses the same output
stream as the main formatter, but in our case, that's a specjour socket
which cannot accept plain-text messages. Just send the summary_stream to
$stderr for now. If you want to see the deprecation warnings, try
running your listeners in the foreground with `specjour listen -f`

sandro/specjour