Remove paredit stuff from prelude-common-lisp.el

The paredit backspace override without having paredit-backward-delete-key defined by paredit was breaking slime loading. I commented this out rather than deleting it since I noticed you had just commented out other paredit stuff elsewhere
Merge pull request #351 from capdevc/patch-1

Remove paredit stuff from prelude-common-lisp.el
Merge remote-tracking branch 'upstream/master'
Merge branch 'master' of github.com:sixpi/prelude