src: allow combination of -i and -e cli flags

If both -i and -e flags are specified, do not ignore the -i. Instead,
launch the interactive REPL and start by evaluating the passed string.

Fixes: https://github.com/nodejs/node/issues/1197
PR-URL: https://github.com/nodejs/node/pull/5655


Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>