Refactor code (#31)

* rename LuaError to Error

* rework try function

* fix docs

* remove table_decoder and list functions

* add table_list_decoder

* improve ffi code

* format ffi code

* rework run function and add exec function

* remove glua/lib/require module

* add docs for returning function and rewrite tests

* improve docs

* rename returning_list to returning_multi

* use returning_multi in tests

* update docs

* clean whitespace in docs

Author: selenil