0.3 ability to close individual/all notifications from code

This pull request is improved from the pull request #239

Needed this functionality on my ajax requests. Open a notification, save that notification on a variable, do stuff and close it.

What i did was, changed the log,error and success notification methods' return value from alertify object to a 0-100 math random number. Random value is used as part of the class name of the notification to be created, and with the closeNow(<last part of the className>) method, i used it to close the dialog i wanted to close. And while i found some time to kill, i added a closeAll() method that closes all open notifications with the same idea.

After that i edited the example page to test, document/explain what i did. Used a minifier to minify the edited js file.

Quick usage:

tempNotification = alertify.log("A persistent nofitication (This one will be closed)", "", 0);
 ... // do stuff
alertify.closeNow(tempNotification); // closes spesific notification

alertify.closeAll(); // closes all of the open notifications.