Cleaning up stdout from R

[pmcq]

We filter out the PIPE_INIT_COMPLETE message from an algorithm's stdout to be a little cleaner, however R prints stuff in a strange format, so doesn't get filtered: [1] "PIPE_INIT_COMPLETE"

https://github.com/algorithmiaio/langpacks/commit/15975004ddf6e9e47744bd95241bb37a075c2da9

More reason to move that message to a separate channel (or to algoout?)