Parse unwind segues

[IvanUshakov]

Hi, I noticed while using that Storyboard Kit did not parse unwind segues. So I add, this ability and some tests.

Please merge it, if it looks normal for you.

[Antol]

I'm also interested in those changes

[yoiang]

Hey @IvanUshakov !
I apologize, I never got the initial notification, I'll check this out ASAP, thank you for the contribution :)

[Antol]

@yoiang BTW there are similar problem with stroryboard links like this:

<!--PMEditProfileVC-->
<scene sceneID="Fap-B1-yVe">
    <objects>
        <viewControllerPlaceholder storyboardName="Settings" referencedIdentifier="PMEditProfileVC" id="pNb-Z8-oMO" sceneMemberID="viewController">
            <navigationItem key="navigationItem" id="CAr-rg-K0G"/>
        </viewControllerPlaceholder>
        <placeholder placeholderIdentifier="IBFirstResponder" id="e7e-IE-MEt" userLabel="First Responder" sceneMemberID="firstResponder"/>
    </objects>
    <point key="canvasLocation" x="1673.5" y="2620"/>
</scene>

[yoiang]

@Antol oh nice, thanks for pointing that out! Could you make another issue to handle First Responder links?
Created #17 !

[yoiang]

@IvanUshakov I apologize, it's been a while since I've used Exit segues! I was wondering how conceptually a segue would be connected to an Exit and thus and Exit Info. It'd be great to have that connection illustrated in the data, your change allows one to create Segues without a destination View Controller but there is no obvious linking to an Exit.

[yoiang]

Also if you merge the latest develop branch into your changes you should get proper build results from Travis!