Option for source_location

I realize this changes the output, but would you be open to including the source_location, is that possible? ie:

```
 % cumulative self self total
 time seconds seconds calls ms/call ms/call name source_location
197.51 16.59 16.59 2 8295.78 8295.78 Thread::Queue#pop /some/gem/file.rb:45
```

I realize there could be multiple source locations for a single `name`.