browsermob-proxy role added

@jzoldak Please review.  Should someone from devops review this as well?


related to https://github.com/edx/bok-choy/pull/53 and https://github.com/edx/edx-platform/pull/4640
Is the current s3 bucket associated with the maintainer of the plugin?  If that's the case I think it may be fine.  Though we may want to host it ourselves for security reasons.