Missing mutable borrows for Table<'lua>

[CXWorks]

Hi,

There may be a Rust violation on changing the value of immutable reference in Table<'lua>.

Its setter methods change the state of self as an immutbale reference.

Could you please help me check if this is a bug or design decision? Thx

https://github.com/amethyst/rlua/blob/262180ff21acf01cdb5c4cb5605feb985bf4d284/src/table.rs#L51-L69

https://github.com/amethyst/rlua/blob/262180ff21acf01cdb5c4cb5605feb985bf4d284/src/table.rs#L228-L241

[CXWorks]

Duplicated by #48

[jugglerchris]

Good job finding the earlier issue!

In case it helps, it sometimes makes more sense thinking of & and &mut as shared/exclusive references, respectively rather than immutable/mutable. It just happens that with simple types it's safe to mutate things you have an exclusive reference to, but Lua types inherently can have multiple references to each other so an exclusive reference doesn't make much sense.