Adding sidebar

I've slightly redesigned the layout of the site by moving the header menu to the left hand side of the screen. You won't see this on mobile, but you will on larger screens.

I also added slash in front of the menu items so that it shows that they are actual folders of the site, such as robin.is/writing.

Overall, this is not a huge change, but I like the altered layout, which I achieved with under 30 CSS statements and almost no HTML changes.

I continue to be amazed at what can be achieved nowadays in CSS without having to alter the HTML, assuming a well structured HTML web page.