Fixing README.md & Adding .gitignore

[mtouzot]

There's a small error (a dash instead of an underscore) in the path to run the CLI.

On my RPi, the setcap command published in the README can't be run as described because of the quote :

(heykube_env) pi@raspberrypi:~/heykube_python $ sudo setcap ‘cap_net_raw,cap_net_admin+eip’ /usr/bin/hcitool
fatal error: Invalid argument
usage: setcap [-q] [-v] (-r|-|<caps>) <filename> [ ... (-r|-|<capsN>) <filenameN> ]

 Note <filename> must be a regular (non-symlink) file.