[maven-release-plugin] prepare release 0.12.0
[maven-release-plugin] prepare for next development iteration
Removing non-exising Netty SockJS dependency.

This dependency will be used later when the SockJS PR is merged into
upstream Netty [1]

[1] https://github.com/netty/netty/pull/1615
assemble standalone jar for server-netty module
Update SockJS CDN URL as is being retired.

Motivation:
The SockJS CDN will retire on 1 Dec 2014 [1] and we need up update our
netty-codec-sockjs and our documentation to reflect this.

JIRA: https://issues.jboss.org/browse/AGSMPLPUSH-68

[1] https://github.com/sockjs/sockjs-client/issues/198