Test 4.2: use the max frame size from the server's SETTINGS frame
Test 4.2: use the max frame size from the server's SETTINGS frame

The test now does a settings handshake and uses the server's settings
to determine the max frame size (then sends a frame 1 byte longer).

Previously the test used the value of the default setting.

rmoorman/h2spec,shane-kearns/h2spec,summerwind/h2spec