We're licensing hte spec under ASLv2. Add the LICENSE file, and add the
short-form to as much of the source as is practical right now (adding it to
json source is a massive pita).
Make the argument to dump-swagger.py be the name of the output file rather than
the output dir, and give it a sensible default.
Also, use the absolute path to the output file, so that the output path is
relative to the user's cwd rather than the templating dir.
