this has actually always been failing to transform the image, but wasn't
being caught by our tests because we are currently only checking the
response code.
This pointer was only needed to pass along the scaleUp option. In order
to prevent someone from specifying the scaleUp option on an individual
request against the owner's wishes, we didn't encode or decode that
field on the Options struct. Instead, we stored the value on the Proxy
object and then set it on the Options struct inside the
TransformingTransport. This worked, but I never really liked binding
those two together.
Instead, we now treat scaleUp as a normal Option field, encoding and
decoding it with all the others. The primary difference is that the
initial value from the request URL will always be overwritten with
whatever is set in Proxy.ScaleUp. This decouples the
TransformingTransport from the Proxy, but prevents the option from being
set in the request URL.
Modifies #37
Remove unused ResponseWriter parameter from check304, add function docs,
and add TODO for alternate Etag header values that we should handle.
Add tests for Proxy.allowed and check304.
