I'm clearly doing something wrong here but--how on earth do I turn tabs on?! Every time I open a new file (cmd-O) it opens in a new window! I've looked through all the menu items, searched the wiki, help *and* the mailing list and but I'm still tab-less. (I'm embarrassed to say I can't figure out how to activate the "dynamic file outline" working either--so I'm actually not able to use features number 1 and 2 on the homepage...)