Switched to company-mode from auto-complete.

company-mode provides better user experience as for me and just works out
of the box. Configuration for it is located in "conf/conf-autocomplete.el"
and includes color theme tweaks to make it look better with my current
solarized-black theme.

I've also sorted out list of packages from "init.el".
- Removed go-mode and clojurescript-mode because I don't use them.
  Marmelade repository has been removed as well for this reason.
- Added smex, paredit, ido-ubiquitous, clojure-mode &
  clojure-mode-extra-font-locking.
- Put description comments for each package.