repl: refactor lib/repl.js

* remove unnecessary backslash (`\`) escaping in regular expressions
* favor `===` over `==`
* multiline arrays indentation consistent with other indentation

PR-URL: https://github.com/nodejs/node/pull/9374


Reviewed-By: Rod Vagg <rod@vagg.org>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Roman Reiss <me@silverwind.io>