Add inputrc binding for yank-last-arg

[christoomey]

With gitsh I find myself very regularly running commands in sequence (specifically diff <fiie> followed by add <file>). Readline has a yank-last-arg function, mapped to M- which for me is alt-shift-- which I find awkward to type. I'd like to bind it, via inputrc for consistency across line-editors, to something more convenient like C-i, or even C-xC-i cause why not go full emacs?

[christoomey]

This is a test