Source map upload using file name of map instead of file name of source

[FDevman]

It looks like this plugin is sending the wrong file name when uploading source maps. I've had source map uploads on deploy via a bash script working for a while now. I've included a screen shot of where it ends up in Raygun. It's not terribly clear from their UI but from experience, that spot is where the URI of the source file belongs but as you can see, this plugin posted the name of the map file.

Unless I'm dead wrong but somehow putting the source file URI there still works anyway.

I'd be happy to write a PR if you will merge it.