Add support for continuation frames on WebSockets

Signed-off-by: John Oliver <johno@insightfullogic.com>
Merge branch 'master' of https://github.com/eclipse/vert.x into websocket-continuation-fix

Conflicts:
	vertx-testsuite/src/test/java/vertx/tests/core/websockets/WebsocketsTestClient.java
Merge pull request #808 from johnoliver/websocket-continuation-fix

Add support for Websocket continuations