Update firebase token in Travis

The deployment token is expired, I think. Deployment fails on travis. We need to update the FIREBASE_TOKEN variable in travis settings. I don't have permissions. Manual deployment still works.

https://travis-ci.org/github/codeforboston/migrant_service_map/builds/759489651

Start with the linked Travis build and the repository's Travis settings. Check the FIREBASE_TOKEN variable and the failing deployment step; done means the token is updated and a Travis deployment succeeds, while noting that the issue reports manual deployment still works and requires permissions to change the setting.

Written by the indexing model from the issue text.