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 

*Technically* they can be, but they don't pass for all browsers yet. That's an ideal goal though, so I'd rather not back in more platform specific things than we need to. :)