It would be useful to add CI for this project since there are decent tests and we want to avoid breakage. One option among others is codeship.com, another popular site that supports bitbucket is drone.io. I played around with codeship.com and it seems fine. Notably - it doesn't require placing a file in your repo like
.travis.yml which I think is a horrible practice.
Unfortunately it doesn't have automatic pull request testing but I don't think any provider has it for bitbucket, but it looks like somebody did try making an easily deployable one on heroku https://blog.codeship.com/build-status-bitbucket/.