Refactor replay

Refactor the replay package.  This change breaks the replay into well separated pipeline stages, namely:

[parse BSON] ---op---> [controlRate] ---op---> [batchOps] ---[]op---> [applyOps]

Each stage controls the lifetime of their own output channels, closing them when appropriate.  Each stage also properly exits early in the case of failure.  The design of the new package is influenced heavily by [this blog post on pipelines](http://blog.golang.org/pipelines)
This update also makes oplog-replay compatible with go 1.3+.
Actually, nevermind, I'm still confused. So if oplog-replay has an error then it will return and we will wait for parseErrors in main which will never happen because done isn't closed and we haven't closed any of the other channels.

Am I missing something? I apologize if I'm being dense.