Adding getGlobalOptions to the Raven object

The thinking here is that this will allow users to pass options to plugins.

We pass back a clone of the options object so that callers can't use this as a back door to mess around with options .

[This jsperf](http://web.archive.org/web/20140328224025/http://jsperf.com/cloning-an-object/2) demonstrates that JSON method of cloning is pretty fast. It kills functions, but I don't think there are any config values that *are* functions, so this shouldn't be an issue.