Preliminary work for lua 5.2
Fixed readme
Exposing method to create LuaError objects (fixes Issue 7)
bugfix: changed semantics of lua_openX calls
open calls for builtin packages debug, bit32 and coroutine
replaced example allocator in example/alloc.go with one that isn't broken
changed PushString and ToString to work correctly when their argument contains NUL bytes
better formatting for contributors list + new contributor
target to link with liblua.a
fix issue #22
merging branch lua5.2 with master