Creating a DSL for our router

This episode is part 8 in the Zero to Framework (building Alchemist Camp) series:

• Part 1 Making a site with just the Cowboy web server
• Part 2: Deploying with Nanobox (which no longer exists 😢)
• Part 3: Building a router and handling static assets
• Part 4: A minimal Plug.Conn clone to handle 404s
• Part 5: Adding EEx templates to a Cowboy web server
• Part 6: Putting an OTP app in our OTP app (pro)
• Part 7: Creating controllers for an Elixir web server
• Part 8: this page

Let's write some macros and make a nice router DSL! Update: Thanks to Micah for pointing out that the var! is unneeded since we don't need to modify conn outside the macro.