Add instrumentation to client.js when running in Node.js

Fixes #5.
Use the native error object if it exists

This improves error reporting in modern browsers.
See http://www.whatwg.org/specs/web-apps/current-work/multipage/webappapis.html
Pass absolute paths to instrumenter

Fixes #95.
Add detailed reporting to runner.js

Fixes #96.
Merge branch 'master' into geezer

Conflicts:
	client.js