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* ``LuaRuntime.require()`` and ``LuaRuntime.globals()`` methods
* renamed ``LuaRuntime.run()`` to ``LuaRuntime.execute()``
* support for ``len()``, ``setattr()`` and subscripting of Lua objects
* provide all built-in Lua libraries in ``LuaRuntime``, including
support for library loading
* fixed a thread locking issue
* fix passing Lua objects back into the runtime from Python space