Support to create Local instance #70

Is your feature request related to a problem? Please describe.
I am not able to create an instance of TrustKit locally just within my library project. It only allows to create a single instance which is shared across the app. So if the app that is using my library also wants to create and configure TrustKit differently, then this could be an issue.

Describe the solution you'd like
TrustKit should allow to create and configure local instances. I see this option is available in TrustKit for iOS.