Fix regression in payday with #2226 chain

The wireup.{billing,nanswers} functions also need an env arg now.
Discovered in #2236.
DRY up the env files

This removes the duplication that existed between defaults.env and
tests/defaults.env. Now the layering is: defaults.env, tests/test.env,
tests/local.env. Paves the way for a reorg of the defaults.env file to
add more comments, etc.
Merge pull request #2242 from gittip/dry-env-files

DRY up the env files
Merge pull request #2241 from gittip/env-fix-payday

Fix regression in payday with #2226 chain
Cache only 200 results in /assets/*.
Cache all assets.
Move all assets to CDN.

Note that while rebasing this commit, I (@seanlinsley) added
a good deal of extra changes since we were still using
the static "/assets/foo" URL in a lot of other places.
Fold chosen.css and reset.css into gittip.scss.
remove unused assets
version all assets

This doesn't version the old widgets because people may still be using
them. (ref: #1767) Except... the first widget refers to an old version
of jQuery that we haven't provided in a long time :-/

This commit also fixes reset.css and chosen.css to correctly load.
remove now-unused `asset_url`

and start using that name for `asset_version_url`
use `asset_url` for elsewhere icons