* add margo_oom setting
* fix returning None
* try not to abort the call early if the mg binary cannot be started correctly
* add basic oom killer
* adjust GOGC (to *try-to* prevent sharp memory rises(which will trigger the oomk))
* raise margo_oom to match margo's default value
* reduce oom poll rate to waste less CPU
* pass margo_oom setting to margo? ... fixes #170
* check if mg binary exists before attempting to execute ti
* ann