adding connect function and fixing subsref#6

Hi Dylan! Thanks for making TIFFStack, I've been using it for analyzing my own imaging data. I had been working with an older version than this repository. I ran into some issues when saving the TIFFStack, but I think you fixed them in a different way now. I created a new function called connect, which performs the connection operations that used to be in the constructor. I did this because after loading the TIFFStack from a .mat, I needed to reconnect. But now it seems that this automatically happens now because you call the constructor again on load (I think). I merged my changes with this version and it seems to still work, just some of the constructor logic is now in the connect function. More importantly, I also slightly changed subsref, to use the varargout and nargout values. I was getting errors before when trying to call the functions (i.e. I was trying to call diagnostic, and subsref was complaining). I think this works a little better, and now you can call the functions like diagnostic or connect. Thanks! Paxon