slides: use IoT-LAB instead of SAMR21
Not sure this is wanted, but I added and replaced some text to use the tutorial on the IoT-LAB instead of using real hardware.
I don't know about this. On one hand side IoT-LAB is available to everyone (or rather should be), on the other hand I know enough people who waited (or are still waiting) for their registration confirmation. Also, we already experienced didactic problems with people who did not realize they were sending packets now over the air instead of simulated via TAP, taking that to the testbed might increase these problems ;-).
I guess the best thing would be to have two alternative versions.
