Use signal.Stop (added in Go 1.1) to clean up state
Improve ReadHistory error messages

Also satisfy golint (errors should not be capitalized)
golint: Document State
golint: Rename timedOut to errTimedOut
golint: uncapitalize error that can't happen
Fix godoc on Windows

Add documentation to input_windows.go as suggested by golint.
Note the reason we ignore golint in input_windows.go