Add 0.0.3-3.rockspec

[heavenshell]

Hi, I like this library.

But, when I ran at MacOSX following error messages were raised.

EXECUTING:  make linux
cd src && /Applications/Xcode.app/Contents/Developer/usr/bin/make linux
/Applications/Xcode.app/Contents/Developer/usr/bin/make all SYSCFLAGS="-DLUA_USE_LINUX" SYSLIBS="-Wl,-E -ldl -lreadline"
gcc -o lua   lua.o liblua.a -lm -Wl,-E -ldl -lreadline 
ld: unknown option: -E
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make[2]: *** [lua] Error 1
make[1]: *** [linux] Error 2
make: *** [linux] Error 2
make lua failed

This is because current 0.0.3-2.rockspec is specified 0.0.3. And 0.0.3 PLATFORM always use 'linux' as platform.

So, I've update new 0.0.3-3.rockspec. Please check, merge and release to LuaRocks repo.