Fix suggested by go vet

[hyangah]

Vet examines the source code and reports suspicious constructs including non-standard signatures for widely-used names such as WriteTo and ReadRune.

$ go vet github.com/chzyer/readline remote.go:276: method WriteTo(w io.Writer) (int, error) should have signature WriteTo(io.Writer) (int64, error) terminal.go:99: method ReadRune() rune should have signature ReadRune() (rune, int, error)

This commit introduces exported method changes.