Reenabling Drone

[kasperlewau]

With Drone dropping the hosted service (https://archive.drone.io) and going open source (https://github.com/drone/drone), I wanted to give it and Coveralls a shot.

My initial setup consisted of setting the COVERALLS_REPO_TOKEN env variable and running nyc on top of my mocha tests as part of my builds on a self-hosted Drone CI.

export COVERALLS_REPO_TOKEN=...
nyc mocha && nyc report | coveralls

This worked just dandy™ - but there wasn't enough data being sent through the coveralls script to coveralls.io to get the status API / automated comments going.

---

This PR re-enables Drone as a CI environment and supplies some more of the available Drone environment data (http://readme.drone.io/0.5/usage/environment-reference/).

• Drone build number
• PR number
• Commit author name & email
• Commit SHA
• Commit message
• Git Branch

So far, I've made one successful build with Coveralls submitting a comment as well as using the Github Status API.

[coveralls]

Coverage increased (+0.1%) to 95.192% when pulling d117e3d on kasperlewau:master into c81c084 on nickmerwin:master.

[coveralls]

Coverage increased (+0.1%) to 95.192% when pulling d117e3d on kasperlewau:master into c81c084 on nickmerwin:master.

[coveralls]

Coverage increased (+0.1%) to 95.192% when pulling d117e3d on kasperlewau:master into c81c084 on nickmerwin:master.

[coveralls]

Coverage increased (+0.1%) to 95.192% when pulling d117e3d on kasperlewau:master into c81c084 on nickmerwin:master.

[nickmerwin]

Thanks @kasperlewau!