Setup CI

I'd be nice to run CI as part of the Cloud Build process.

I'm running `go test` and getting:
```
clone_test.go:94: clone(git@github.com:google/new-project.git) error = git clone failed: exit status 128, output:
Cloning into '/tmp/git-clone-test475820070/test-3'...
git@github.com: Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.
, wantErr false
```

This is because I don't have an SSH key setup. It might be acceptable to instead use `git://github.com/google/new-project.git` but then we wouldn't be testing SSH cloning. To automate testing of SSH cloning we'd need to have a test account with an SSH key and have that key setup on the CI machine.