Initial implementation of stream accumulation
Initial implementation of stream accumulation

Fixes #249

captainsafia/nteract,rgbkrk/nteract,temogen/nteract,temogen/nteract,0u812/nteract,jdfreder/nteract,nteract/nteract,0u812/nteract,rgbkrk/nteract,jdetle/nteract,jdfreder/nteract,nteract/nteract,jdfreder/nteract,nteract/nteract,rgbkrk/nteract,captainsafia/nteract,rgbkrk/nteract,jdetle/nteract,0u812/nteract,captainsafia/nteract,nteract/nteract,captainsafia/nteract,jdetle/nteract,jdfreder/nteract,nteract/composition,temogen/nteract,nteract/composition,jdetle/nteract,0u812/nteract,nteract/composition,nteract/nteract,rgbkrk/nteract