Don't run site tests under Java 8 for now (#421)
Convert TestHttpClient to be based on the ratpack httpclient

Add autoclosable to the TestHttpClient, DefaultTestHttpClient, and BlockingHttpClient

Change TestHttpClient to be based around actions configuring the request.
Set timeout on blocking httpclient latch so bad request specs don't hang the testing.
Core tests passing

Added cookie support to the DefaultTestHttpClient