Move examples from README.md to godoc

[alanconway]

Go supports testable examples https://blog.golang.org/examples. They have important advantages over README examples.

1. more visible - the examples end up in the package godoc, where they are more likely to be found by package users.
2. better tested - examples become tests, run by "go test". Immediate warning if a change breaks an example, and as a bonus it counts to test coverage.

[n3wscott]

Cool idea!!!

I have not really known how to get the examples in shape. Want to migrate one and see what it looks like and show the path?

[alanconway]

Will do.