add support for node.js to act as a socket client
updated library_sockfs.js to make WebSocket a local var and updated library_browser.js to modify requestAnimationFrame to provide a fallback to setTimeout if window is undefined
replace window.WebSocket with window['WebSocket'] to avoid closure compiler issues
moved nodejs client test case into main sockets test class as requested. Run with ./runner.py sockets.test_nodejs_sockets_echo
Removed RunnerCore import as no longer needed and added return self.skip('node is not present') to test_nodejs_sockets_echo if node isn't available
Merge pull request #1743 from fadams/fix-nodejs-socket-client

add support for node.js to act as a socket client