Add support for CircleCI commenting on PRs

[saponifi3d]

This adds support for node-coveralls to post the service_pull_request for CircleCI.

• Unfortunately they don't have an environment variable that is the PR number itself, so there is minor string manipulation to get it working.

[coveralls]

Coverage decreased (-0.41%) to 95.26% when pulling fba9005 on saponifi3d:circle-pr-support into d5e1372 on cainus:master.

[saponifi3d]

FYI - there is something funky in the test harness, it's failing because travis is setting the env variable?

[dougmoscrop]

Any progress on this? We'd really like to use coveralls with CirlceCI.

[saponifi3d]

I'm just using this fork for now. Works great, the rest failure is a weird env variable that breaks on travis.

[nickmerwin]

Thank you @saponifi3d !