Don't use ido-completing-read, let the users decide

[Tu Do]

Here: https://github.com/chrisbarrett/emacs-refactor/blob/master/emr-c.el#L127.

Please make it completing-read, or at least when ido-mode variable returns t.

[Tu Do]

We should do similar to Projectile: let user chooses their completion system. By default, we use Ido, but leaving Helm as an option.