Means `datasette publish heroku` can work under Travis, unlike this failure:
https://travis-ci.org/simonw/fivethirtyeight-datasette/builds/488047550
```
2.25s$ datasette publish heroku fivethirtyeight.db -m metadata.json -n fivethirtyeight-datasette
tar: unrecognized option '--exclude-vcs-ignores'
Try 'tar --help' or 'tar --usage' for more information.
▸ Command failed: tar cz -C /tmp/tmpuaxm7i8f --exclude-vcs-ignores --exclude
▸ .git --exclude .gitmodules . >
▸ /tmp/f49440e0-1bf3-4d3f-9eb0-fbc2967d1fd4.tar.gz
▸ tar: unrecognized option '--exclude-vcs-ignores'
▸ Try 'tar --help' or 'tar --usage' for more information.
▸
The command "datasette publish heroku fivethirtyeight.db -m metadata.json -n fivethirtyeight-datasette" exited with 0.
```
The fix for that issue is to call the heroku command like this:
heroku builds:create -a app_name --include-vcs-ignore
