Fixed dropped Twitter error code 89 when using a revoked token

When the user revokes an app access token, subsequent attempts to use the token result in an HTTP 401 response that omits the WWW-Authenticate header, required for HTTP 1.1 as detailed in RFC 2616.  This causes an IOException from HttpUrlConnection, and a general TwitterException occurs that obscures the error code 89 (Indeed, the response body is not parsed before the IOException occurs).

See https://dev.twitter.com/issues/1114