Remove ToStr impls
Remove ToStr impls

Latest rustc now impls ToStr for all Shows.

tempbottle/rust-lua,kballard/rust-lua,trevex/luajit-rs,tempbottle/rust-lua,beatgammit/rust-lua,kballard/rust-lua,beatgammit/rust-lua,green-panther/rust-lua,green-panther/rust-lua,trevex/luajit-rs