Added significantly improved pylambda test script
Added significantly improved pylambda test script

Now, calling sframe.sys_util.test_pylambda_worker() runs both
simulated and unsimulated pylambda worker tests, packages all logs
into a zip file, and prints the name of that zip file.  Users having
pylambda issues can then submit this zip file to allow us to debug.

haijieg/SFrame,turi-code/SFrame,dato-code/SFrame,dato-code/SFrame,haijieg/SFrame,TobyRoseman/SFrame,TobyRoseman/SFrame,turi-code/SFrame,ylow/SFrame,TobyRoseman/SFrame,turi-code/SFrame,hoytak/SFrame,dato-code/SFrame,dato-code/SFrame,TobyRoseman/SFrame,hoytak/SFrame,hoytak/SFrame,hoytak/SFrame,TobyRoseman/SFrame,haijieg/SFrame,dato-code/SFrame,ylow/SFrame,ylow/SFrame,haijieg/SFrame,hoytak/SFrame,turi-code/SFrame,dato-code/SFrame,TobyRoseman/SFrame,turi-code/SFrame,TobyRoseman/SFrame,haijieg/SFrame,ylow/SFrame,haijieg/SFrame,ylow/SFrame,hoytak/SFrame,haijieg/SFrame,hoytak/SFrame,ylow/SFrame,ylow/SFrame,dato-code/SFrame,hoytak/SFrame,turi-code/SFrame,dato-code/SFrame,haijieg/SFrame,turi-code/SFrame,TobyRoseman/SFrame,ylow/SFrame,turi-code/SFrame