Added common ignore globs for Lua, an extensible, high-performace, lightweight multi-paradigm language designed for embedded scripting.

    http://www.lua.org/about.html (More info at https://en.wikipedia.org/wiki/Lua_(programming_language) )

The de-facto package manager for Lua is LuaRocks.

   http://luarocks.org/

- LuaRocks creates a number of files as part of the build process.  These are ignored (*.src.rock, *.tar.gz, *.zip)
- Lua modules are conventionally written in C as shared libraries.  Common build artifacts for C projects copied from C.gitignore