Code review comment for lp://staging/~thomas-voss/net-cpp/bug-fixing-and-features-landing

@Gary: I changed a few minor things when compared to your MP:
  - pause/resume on the easy handle is invoked on the downloading/uploading thread now.
  - fixed the test case to talk to a server that is (hopefully) reachable from within our CI labs.
  - some packaging updates to account for the major version bump.
  - moved speed.{limit, duration} into the Request::Configuration struct, picking reasonable values by default.