https://github.com/scalaz/scalaz-stream/issues/132 https://github.com/scalaz/scalaz-stream/issues/132 unsafeChunkR doesn't actually reuse the same buffer.
minor efficiency change, do the length test first (and use `array.length` rather than `.size`)
Merge pull request #158 from jedws/master

unsafeChunkR doesn't actually reuse the same buffer.