* Adds IPRO tests that we should have copied from apache_system_test.sh back
when we first added IPRO.
* The "IPRO-optimized resources should have fixed size, not chunked" test
fails. The problem is as it says: IPRO optimized resources are being sent
out with `Transfer-Encoding: Chunked` instead of `Content-Length: ...`. How
do we fix this?
* install/system_test.sh moved to net/instaweb/automatic/system_test.sh
* minor method signature changes
* url.is_valid() is gone, replaced by .IsWebValid()
* I pushed Otto's #464 upstream, and now we need to make some IPRO changes.
* beacons have nonces now, so we need to update tests.
Otto van der Schaaf