Kill child process when socket disconnects

[mbhall88]

When the websocket is closed, i.e if the client navigates away from the page during analysis, kill the child process.
Should be able to just add a 'disconnect' listener to the socket.

[mbhall88]

Functionality is there but now there is a problem where if the client clicks 'Stop Analysis' button and then closes the browser there is an error because the 'disconnect' event on the socket is trying to kill the child process and writeStream when they were already stopped by the 'kill' event emitted from the client-side.

[mbhall88]

This has now been fixed. On socket disconnect event there is a series of logic steps which will close the child process and/or writable streams if they're still open:

socket.on('disconnect', function(){
        console.log("Socket disconnected");
        // TODO - run test to see if CP and stream are already closed
        if (writeAnalysisFile.closed && !speciesTyping.connected){
            // write stream and CP are both closed.
        } else if (writeAnalysisFile.closed && speciesTyping.connected) {
            // write stream closed but CP open still.
            onCloseOrKill(speciesTyping.pid, null);
        } else if (!writeAnalysisFile.closed && speciesTyping.connected) {
            // write stream and CP both open.
            onCloseOrKill(speciesTyping.pid, writeAnalysisFile);
        } else {
            // write stream open but CP is closed.
            onCloseOrKill(null, writeAnalysisFile);
        }
    });