refactoring out single io thread to multiple threads
refactoring out single io thread to multiple threads

rsmith31415/sh,simudream/sh,pdelong42/sh,jakirkham/sh,hacosta/python-sh,z-fork/sh,lwgarmstrong/sh,Stupeflix/sh,pombredanne/sh,amoffat/sh,achernet/sh,rdhyee/sh,germangh/sh,hacosta/python-sh,twocngdagz/sh,amoffat/sh,ppannuto/sh