[Test only] Move deflate tests from PerMessageCompressTest to PerMessageDeflateTest
[Test only] Move deflate tests from PerMessageCompressTest to PerMessageDeflateTest

- empty message test
- message with null character test

After clean up, we'll delete permessage-compress support and
PerMessageCompressTest

R=yhirano@chromium.org

Review URL: https://codereview.appspot.com/97700043
google/pywebsocket,GoogleChromeLabs/pywebsocket3,GoogleChromeLabs/pywebsocket3,GoogleChromeLabs/pywebsocket3,google/pywebsocket,googlearchive/pywebsocket,googlearchive/pywebsocket,google/pywebsocket,googlearchive/pywebsocket