Fix wifi-cfg call

[sgallou]

Just a very small fix to the readme about the wifi-cfg call.

[TheSin-]

do you really need bash in there? can't just call sudo /usr/bin/wifi-cfg ?

[sgallou]

It tried it, but it doesn't work.
I can not verify right now (I'm not at home), but I think script is not executable. And it's much easier to call it with bash instead of doing a chmod +x previously. But it's just my opinion.