Fix timeout in twisted adapter

Both callLater and add_timeout accept number of seconds until timeout,
no need to substract current time.
removed call to cleanup from Channel._shutdown
Pass milliseconds to poll
Fix channel._on_close() without a method frame.

If a channel close is triggered by connection close which doesn't have a
method_frame (eg, because of a socket disconnection due to missed
heartbeats), channel._on_close() will be called with a method_frame of
None.  This patch handles this, to avoid looking up attributes on None.
Merge pull request #276 from rboulton/channel_onclose_fix

Fix channel._on_close() without a method frame.
Merge pull request #274 from cellscape/pass-ms-to-poll-268

Pass milliseconds to poll
Merge pull request #270 from cellscape/fix-twisted-add-timeout

Fix timeout in twisted adapter
Merge pull request #272 from atatsu/cleanup-breakage

removed call to cleanup from Channel._shutdown