Linux version added

I have added the Linux version of Hack, Slash, Loot to Steam. It is missing the Steam specific features, most notably Achievements, but in all other ways it is the same as the Window and Mac OS X versions.

Head over to the discussion boards if you have any issues. It's tested on Ubuntu and SteamOS, but obviously there are many more flavours of Linux and I couldn't test them all.

Enjoy ːboykingː