repl: add mode detection, cli persistent history

this creates a new internal module responsible for providing
the repl created via "iojs" or "iojs -i," and adds the following
options to the readline and repl subsystems:

* "repl mode" - determine whether a repl is strict mode, sloppy mode,
  or auto-detect mode.
* historySize - determine the maximum number of lines a repl will store
  as history.

The built-in repl gains persistent history support when the
NODE_REPL_HISTORY_FILE environment variable is set. This functionality
is not exposed to userland repl instances.

PR-URL: https://github.com/iojs/io.js/pull/1513


Reviewed-By: Fedor Indutny <fedor@indutny.com>