Also search for HL in $HOME/.steam/root/SteamApps

This covers non-standard install locations for Steam.
Not sure if there is a way to get to any additional Steam library
folders.
Escape $@ when writing the runscript
Don't hardcode the HL location in the runscript

Otherwise it will stop working after moving the Steam/library dir.
Merge pull request #1 from dscharrer/install_script

Minor problems in the install script