Add CPPodfileConsoleTextView to allow auto scrolling

[aaronpearce]

Fixes #188 by adding CPPodfileConsoleTextView to allow the text view to automatically scroll to the bottom if it was previously there.

I attempted to do this scrolling via utilizing NSTextView delegate methods on CPPodfileConsoleViewController but none of them had the right order of completion. We must check current position, then append text and then scroll for this action to function correctly.

To do this, I have added an attributedText property to the CPPodfileConsoleTextView subclass (couldn't override attributedString directly). On didSet we check the current position then swap out the actual attributedString on the text storage and scroll to the previous positioning.

There may be a simpler way to do this than subclassing and adding a property but I couldn't work it out. If anyone has a suggestion on a cleaner way to implement this, I'm happy to give it a shot.

[orta]

AWESOMEEEE

[orta]

I think this looks great, thanks a lot @aaronpearce