Make the list of modules loaded by Prelude configurable.

Modules loaded by Prelude can now easily be adjusted via
the file `prelude-modules.el` in Prelude's installation folder.
To disable a module simply comment it out; conversely uncomment
a module to enable it.

sample/prelude-modules.el

@@ -0,0 +1,24 @@
+;;; Uncomment the modules you'd like to use and restart Prelude afterwards
+
+(require 'prelude-c)
+;; (require 'prelude-clojure)
+;; (require 'prelude-coffee)
+;; (require 'prelude-common-lisp)
+;; (require 'prelude-css)
+(require 'prelude-emacs-lisp)
+(require 'prelude-erc)
+;; (require 'prelude-erlang)
+;; (require 'prelude-haskell)
+(require 'prelude-js)
+;; (require 'prelude-latex)
+(require 'prelude-lisp)
+;; (require 'prelude-markdown)
+;; (require 'prelude-mediawiki)
+(require 'prelude-org)
+(require 'prelude-perl)
+;; (require 'prelude-python)
+;; (require 'prelude-ruby)
+;; (require 'prelude-scala)
+(require 'prelude-scheme)
+;; (require 'prelude-scss)
+(require 'prelude-xml)