Issues with deploy via subtree

We were just recently trying to deploy with the instructions provided by the README and `bin/deploy`. Unfortunately, since the `build` folder is being ignored from git, `git subtree push --prefix build origin gh-pages` just keeps pushing the last version of build that was ever committed.

Removing `build` from the gitignore resolves this issue. However that doesn't feel like the best solution. I'm not sure what the best solution to resolve this is just yet.