Integrate brakeman security scans to our Travis CI checks

[giacoelho]

Summary

We should run security scans to our TravisCI checks to better ensure we don't introduce security vulnerabilities. Let's update our Travis configuration to also run these checks and let us know if we should fix any vulnerabilities. We just got a pr for this on the diaper app and need it added here too.

https://brakemanscanner.org/docs/quickstart/

Criteria for Completion

• TravisCI tests should fail if a pull request has a security vulnerability

[andersonfernandes]

Hi @designbygia, can I work on this issue?