Fix for WebKit Issue #31

[wied03]

Fix for #31

• Run the browser test in Firefox and Webkit and ensure that works right to prevent this from happening again
• Handle Webkit/Firefox stack traces properly
• If we don't match again, fail more gracefully since this is not a 'test should stop' type failure

[wied03]

@elia - Can you release this as 0.5.0.beta2 ASAP? It might be overkill to even have an implementation of Kernel::caller, but at least now it won't throw if it can't parse.

[elia]

@wied03 released: https://twitter.com/rubygems/status/633050314992676864