9/27/17 Now has a hinge and a lock that holds everything in place. The cards will never come out on their own now. The hinge is made out of a piece of 1.75 mm filament
8/6/17 I updated the model, the lock is now just a constant amount of force instead of sliding it up and down to lock/unlock. This just makes it easier to print while still being able to hold the cards in place. There are also some different versions of it with different thickness of the case so you can have one that is more sturdy if you would like.
This the new version of my original design, linked here: http://www.thingiverse.com/thing:1648262 (Check it out to see how it was made and how to use it)
Also, it now adds a money clip on the front of the wallet