Increase compatibility with Rollbar API

[ecton]

First, I removed code field as per RoxasShadow#13. Based on the Rollbar engineer's comment, since we don't have access to the source code, we should be omitting this value.

However, I was still having grouping issues. In reading through the errors and looking at the settings in Rollbar, i determined that the exception.class field being set to the Thread's name is what was causing the grouping errors.

Unfortunately, typename is deprecated because a new feature was added to rust 1.38 giving an official way to get the name of a type. I added the usage of this new feature, but that means that if this is merged, there's a new requirement on Rust 1.38 and it appears there's not a way to currently specify that in the Cargo.toml.

I'll be creating an MR back to the main branch with these changes, but I'll also publish a tag if someone wants to use a git ref to refer to my repo.

[ecton]

Unfortunately I can't get Github to realize the first two commits were already on my master. The only set of changes for this is: f0d4585

I unfortunately based this branch off of the previous fix I made and didn't push my master before creating the MR.