Update README.md

[jsjrobotics]

On latest Raspbian, had to run scons not scons build to compile

[Gadgetoid]

Thank you! Although if you're using the Unicorn HAT with C, you might as well skip right to the upstream version of rpi_ws281x here: https://github.com/jgarff/rpi_ws281x

Edit: Looks like the C example clones and builds an old build from our up-to-date fork of that repository. I should probably update it.