Fixed missing path to the lib sodium (required at least for Ubuntu 13.10).
Updated readme with the same path and version of sodium as in the
install script.
Added a gitignore file (ignore the binaries).
Client can now be added and then removed without introducing characters in the
black/whitelist files.
Do not add client more than once.
If client is found in list, stop directly the scan.
When scanning if client is added, do not just compare the beginning
of the username, e.g. 'user1' and 'user12' is not the same user.