Allow LivefyreStreams to stream reply Content, not just top-level

Previously, `streamhub-sdk/streams/livefyre-stream` and `streamhub-sdk/streams/livefyre-reverse-stream` would only emit Content that was top-level. Reply Content would be added to the replies array for the parent content.

However, one may want to use the Stream to source Content to display as a flat list, ignoring replies and threading.

With this change, the two streams can be constructed with an option, `replies`. If `replies` is truthy, then the stream will emit reply Content, not just top-level Content.

Because options to `StreamManager.create.livefyreStreams` are proxied to both streams, the `replies` option can be provided there as well. So to create a StreamManager with forward and reverse streams that emit replies:

    var streams = StreamManager.create.livefyreStreams({
            "replies": true,
            "network": "labs-t402.fyre.co",
            "siteId": "303827",
            "articleId": "sh_col_51_1366914813",
            "environment": "t402.livefyre.com"
    });