Drop node 4 support, add node 10 and latest
Drop node 4 support, add node 10 and latest

Seems like the peer dep resolution in npm 2.15.11 is buggy,
so it cannot find a solution to this dilemma:

    npm ERR! node v4.8.4
    npm ERR! npm  v2.15.11
    npm ERR! code EPEERINVALID

    npm ERR! peerinvalid The package unexpected@11.0.0-4 does not satisfy its siblings' peerDependencies requirements!
    npm ERR! peerinvalid Peer unexpected-mitm@12.2.1 wants unexpected@^10.27.0 || ^11.0.0-3
    npm ERR! peerinvalid Peer unexpected-messy@8.2.1 wants unexpected@^10.27.0 || ^11.0.0-3
    npm ERR! peerinvalid Peer unexpected-express@11.1.1 wants unexpected@^10.27.0 || ^11.0.0-3
    npm ERR! peerinvalid Peer unexpected-http@6.1.0 wants unexpected@^10.27.0 || ^11.0.0-4

Besides, unexpected-mitm 12 no longer supports node 4, so it wouldn't
work anyway.

alexjeffburke/unexpected-couchdb