PWMScanner - minimum strength does not work

[GrahamCobb]

The main processing loop does not ignore packets with less than the minimum signal strength.

Let me know if you need a pull request, but the fix is straightforward. After the call to showStatus() add:

            strength= 0 - ord(str(d.getRSSI()))
            if strength < minimumStrength:
                    continue

[keldnorman]

To get the PWMScanner to work I altered around line 122

FROM
sys.stdout.write(spinner.next())
strength = 0 - ord(str(d.getRSSI()))
sigFound = "0"
TO:
sys.stdout.write(spinner.next())
try:
strength = 0 - ord(str(d.getRSSI()))
except:
strength = 0
pass
sigFound = "0"