Add option to leave .emacs alone

[paxperscientiam]

IMO (ha), moving .emacs is unnecessarily opinionated. I already use chemacs for managing multiple emacs installations. Given this and that prelude already provides for installing somewhere other than ~/.emacs.d, the installer should provide an option to leave .emacs alone.

Definitely something I could contribute.

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contribution and understanding!

[bbatsov]

PR welcome!