Add a "make test" target that builds and tests everything
Revert "Have run_tests.sh run the unit tests as well"

This reverts commit 88544ea99a26e30467cf69f8a70ab032b888da78.

We now have "make test" so this is redundant
Move read loop into the handler
Inline handler_process_bytes so we can more cleanly handle out-of-buffer situations
Fix "make test" target
Break out response buffering and sending into a separate unit