Add reference to code examples

[cygnet3]

Add reference to the sp-examples repo in the README (and that these are still heavily under construction)

[nlanson]

Why not put examples in the repo under examples/?

[cygnet3]

Why not put examples in the repo under examples/?

I guess that can be done too. Right now I have a couple of files in a different repo (https://github.com/cygnet3/sp-examples). I wanted to link to that repo in the README once those examples are a little more fleshed out, but I can also add them to a examples/ folder indeed!