Layout Demo issues

[sondresj]

• The View Source link is broken (the blue github icon), set srcPath='Layout.tsx' on the DemoTitle
• The property screenSize isn't a property the user needs to provide, the Layout component get's it from the withScreenSize HOC wrapped around it.

You could also add a text saying that this (the github page) is using the Layout, something along the lines of 'This page is using the Layout component, view the code using the Layout <Link href='https://github.com/tfso/react-tfso-components/blob/master/src/demo/Layout.tsx'>here</Link>'

Otherwise good work! 👍