Using both user name and email for gh-pages commits.

The Travis logs indicate git is hinting that both an
email and a name should be set:

```
Update docs after merge to master.
 Committer: selfiebot <travis@testing-worker-linux-docker-981a76b7-3328-linux-4.prod.travis-ci.org>
Your name and email address were configured automatically based
on your username and hostname. Please check that they are accurate.
You can suppress this message by setting them explicitly:
    git config --global user.name "Your Name"
    git config --global user.email you@example.com
After doing this, you may fix the identity used for this commit with:
    git commit --amend --reset-author
```

From https://travis-ci.org/GoogleCloudPlatform/gcloud-python/builds/44498713