Don't compile tests to JS unnecessarily.

Support http_parser 1.0.0.

Fix a broken link in the README.

Add a hacky hook to override the loader behavior.

This is specifically to allow Sky to get sky_shell support into the test
runner immediately. It's temporary; it'll last until we land proper
plugin support.

See dart-lang#320

R=rnystrom@google.com

Review URL: https://codereview.chromium.org//1309493002 .

Widen the Dart SDK constraint to include `1.13.0`.

Make source maps work properly in the browser.

Fix a memory leak in browser tests.

Narrow dependency constraints to remove hacks.

Browser debugging support.

Widen the constraint on `analyzer` to include `0.26.0`.