Add specs for streaming http responses
Pending specs for more reasonable streaming behaviour

Previously, errors in subsequent chunks were caught and then the whole
request was retried, yielding (possibly) repeated chunks to the
read_block, without any indication (in the block) of this being done.

The outer client method would also not report any errors for a consumer
to check.
Disable retries as soon as any data has been yielded
Merge pull request #283 from grddev/spec_streaming_http

Spec somewhat reasonable error handling for streaming http responses