The Instrumental class constructor should accept config options

[tonydewan]

We're using the Instrumental class directly in a project (we need 2 instances of the agent side by side), and it's annoying to have to call configure separately. We can't chain the call to configure (i.e.,I = new Instrumental().configure({...})) since it doesn't return the instance. That means we've got to call configure separately for both instances.

It seems like the best option is to allow the constructor to optionally take config options.