Use stable versions of crucial Clojure packages

I cleared out my `elpa` directory and started fresh - everything seems to work and the errors caused by the mismatch between the Emacs CIDER and installed CIDER are gone.

Sadly pinned packages only work as long as you're using a pretest version of Emacs 24.4; the variable will just be ignored for anyone with an outdated Emacs. Added ignore-errors just to be safe though.