IllegalStateException on 1xx response codes

[wirelessMousetail]

Looks like there is no support for 1xx responses - Illegal state exception is thrown by Feign on any response with code less than 200 during response building:
https://github.com/OpenFeign/feign/blob/master/core/src/main/java/feign/Response.java#L47

[rage-shadowman]

I wonder why it checks at all. It doesn't check for >= 600 (which is where all the status lists I see stop).

[kdavisk6]

This seems like a fairly simple change. There are enough checks in the Client that the additional check when creating the response seems unnecessary. Since the body can be null, we should be able to support 1xx responses.