Fix traceback parsing under Safari.
Fix traceback parsing under Safari.

Safari (possibly just Safari 6) ends up in the Firefox traceback parser. This
actually works with two minor fixes:

- Function arguments are not supplied so don't attempt to parse them out.
- Tracebacks appear to end in a '[native code]' entry. Deal with this.

chrisirhc/raven-js,malandrew/raven-js,vladikoff/raven-js,Mappy/raven-js,getsentry/raven-js,eaglesjava/raven-js,danse/raven-js,Mappy/raven-js,housinghq/main-raven-js,benoitg/raven-js,Mappy/raven-js,malandrew/raven-js,grelas/raven-js,danse/raven-js,housinghq/main-raven-js,housinghq/main-raven-js,PureBilling/raven-js,iodine/raven-js,samgiles/raven-js,getsentry/raven-js,janmisek/raven-js,samgiles/raven-js,iodine/raven-js,grelas/raven-js,clara-labs/raven-js,hussfelt/raven-js,eaglesjava/raven-js,vladikoff/raven-js,clara-labs/raven-js,janmisek/raven-js,PureBilling/raven-js,chrisirhc/raven-js,getsentry/raven-js,getsentry/raven-js,benoitg/raven-js,hussfelt/raven-js