Increase Test Coverage

[Sherlouk]

We should increase the test coverage to demonstrate more real-world examples as opposed to flat blue blobs (which I'm pretty sure are against Apple's HIGs and wouldn't be allowed in production).

I want to demonstrate (and then document with images in the README) various different use cases including:

• Different Themes (A view controller which responds to light/mode dark)
• Different Localisations (A view controller which changes based on the user's locale)
• Different Accessibility Modes (A view controller which supports dynamic text sizes, smart invert, etc)
• Different Devices (A view controller which changes depending on the device or screen size)
• Different Sizes (A view/cell which changes based on the rendered size)

other ideas welcome

I also want to add some extra tests including:

• A performance test covering the entire stitch strategy
• A test which uses a custom strategy which adds random timeouts to the snapshots (and as such will return out of order - testing our sorting solution)
• A test which checks the title trimming approach
• Tests to cover independent units of code throughout the package (especially the calculateImageSize function)