Fixing timing issue with resetting Esplora 

- it appears that at least on a Mac some assumptions about Esplora are slightly different:
  * there are two usb serial ports, not one (cu.xxx and tty.xxx)
  * after sending 1200 baud to the COM port it takes no time for ports to get reset, so our checks
    are not registering any disappearing ports in this case even at 10ms interval. Worked around
    by switching this into a WARNING and allowing to continue after 2 seconds of trying, which leaves
    another 6 seconds on Esplore, in the case when reset actually worked (for me 100% of the time).