[REQ] Add response header deserialization

[spacether]

Is your feature request related to a problem? Please describe.

Add response header deserialization

Describe the solution you'd like

Response headers should be accessible and their values should be schema instances

Describe alternatives you've considered

Additional context

[spacether]

An initial implementation for json header params was added in #47
But no work was done to ensure that the source header data was encoded properly
Headers do not allow in all utf-8 chars, so that will need to be improved in the future
Perhaps header json should be percent encoded like query string json

[spacether]

Feature is available in the 2.0.0 release