Can't add request that contains "/" in name

[ThePhilgrim]

When I add requests, I sometimes want to name them after the url, e.g. localhost:3000/foo.

This creates an error message
Error invoking remote method 'renderer:new-request': Error: ENOENT: no such file or directory, open '/Users/path/to/collection.bru'.

[Its-treason]

The request name is also the file name and / is not allowed as a file name.

We already have a PR open to fix this #349 but not sure when it gets merged.