CI builds always say wattsi is out of date

[domenic]

Example: https://travis-ci.org/whatwg/html/builds/385218917

This is because when we create Wattsi, we try to set the version using git. But, inside the build process's docker container, we've exluded the .git directory (to increase determinism). So, setting the version always fails, and thus checking it later always fails.

Will have to think on what the right solution is here.