Add emacs and more tools to /tools/; fix a typo

Staged at:

http://tools.dart-lang.appspot.com/tools/

I'm not thrilled with putting "More tools" under "Tips", but I think it'll do for now. In the future, we might want to remove the hero head, consider using tabs, and change the 2 download columns to be something else (such as official Darty goodness vs. other Darty goodness).

BUG=9942

Review URL: https://chromiumcodereview.appspot.com/18699005