v0.8.1 - getLayer API and bug fixes

• added a new API get_layer, which returns a layer object that would return the correct parameter value for the given user within the layer, no matter which experiment the user is allocated to within the layer;
• fixed a bug where time was not added to events;
• fixed a bug where /get_config fallback was not correctly called in the event that the SDK does not know how to evaluate a rule locally.