Use scss-mode instead of web-mode for SCSS files
Remove some global externs for js2-mode
Update for Emacs 24.4

* Uniquify is now enabled by default.
* Remove custom lambda prettifying; use the new Prettify-Symbols mode
  instead.
* No need to check for leuven-theme, as it is included by default.
* Electric Indent mode is now enabled by default, so `C-j' won't indent
  the newline like `RET' does. Make them equal.
* `turn-on-eldoc-mode' is obsolete; use `eldoc-mode' instead.