v2.0.0

• Major refactor and simplification into generic REST client.
• API parameters are now passed as a map to endpoint handlers.
• User-Agent is now set to track client usage and help debug issues.
• generateTelesignHeaders is now static and easily extracted from the SDK if
  custom behavior/implementation is required.
• Now using OkHttp to perform web requests, handle connections and reconnects, ssl negotiation and reduce code