Notify user Tor mode is activated in shell prompt

Notify user if Tor mode is activated in shell prompt by adding a line to .bashrc

# user@computer:~$ . torsocks on
# Tor mode activated. Every command will be torified for this shell.
# (tor) user@computer:~$ 

# (tor) user@computer:~$ . torsocks off
# Tor mode deactivated. Command will NOT go through Tor anymore.
# user@computer:~$