clarify modules are Lua, need LMOD

+Modulefiles for loading and unloading the sbgrid or biogrids environment are available in /programs/share/modulefiles/x86_64-linux and /programs/share/modulefiles/i386-mac. The module files are Lua format and should work with an existing LMOD installation. Loading the sbgrid/biogrids module initializes the entire sbgrid/biogrids environment and is used instead of the "source" command. If you are using modules then you should remove the source lines, such as "source sbgrid.shrc", from your startup rc files.