slightly imprecise installation instructions

At http://arduino.cc/playground/Linux/Ubuntu

under "All Ubuntu versions (old and new) can get the newest packages from Debian Sid", it says:

Download arduino and arduino-core .debs into a clean directory from: http://packages.debian.org/sid/arduino-core http://packages.debian.org/sid/arduino (Uno/Mega2560 owners also need http://packages.debian.org/sid/librxtx-java)

Indeed, everybody also needs librxtx-java, as it is a dependency of the arduino package, which will refuse to install if you don't have the librxtx-java package installed