swift-simulator: avoid hard-coded URLs
swift-simulator: avoid hard-coded URLs

To gather coverage data, we will be running the tests from a different
directory (since the JavaScript files will be copied to another folder
when they're instrumented by Istanbul).

So the simulator now uses the same logic as the Swift service to
determine account URL.

zerovm/swift-browser,zerovm/swift-browser,mindware/swift-browser,mindware/swift-browser,mgeisler/swift-browser,mgeisler/swift-browser