don't remove anonymous functions from stack trace

TraceKit's stacktrace regex for Chrome didn't match anonymous functions, so all anonymous functions in the stacktrace were being removed before reporting to Sentry.  This caused errors to be attributed to the wrong files, and was generally extremely confusing.  This change updates the regex to not *require* a function name be present in the stacktrace.

see #289 

I wrote it that way because I assumed it'd be run from the command line only, through v8, so it would act just like Chrome.  But that might be a bad assumption!  I don't know Mocha very well.  I'm guessing from your comment that the tests can be run in-browser too.