[Mac] Starting new conversations sometimes fails to bring the message window to the front

Unless starting the conversation opens a chat window (i.e. is the first conversation) it won't bring the window to the front. Adding

if(Spark.isMac()) {
toFront();
}

at ChatFrame.java:150 (bringFrameIntoFocus) fixes this issue, but I haven't tested it thoroughly to see if it incorrectly brings it forward in other cases.