Update Error Handling

[MrAlias]

• Remove any one off error handlers, replacing, instead, with the global.Handle function.
• Update tests to support new error handling.
• Add error handling in the span SetName when span is uninitialized.

Closes #174

[jmacd]

Someday, someone will come along and ask why it's not possible to have per-SDK error callbacks. I propose we wait for that to happen. This is great.

[Aneurysm9]

Someday, someone will come along and ask why it's not possible to have per-SDK error callbacks. I propose we wait for that to happen. This is great.

I was thinking the same thing myself, also that I don't think it's possible to change the global handler once one is set. But, I can't point to a use case for that and it's definitely something that can be changed if needed down the road.