Istanbul configuration for Coveralls via Travis

.travis.yml

before_script: 'npm install -g istanbul && npm install -g mocha'
script: 'make test-cov'
after_success: 'make coveralls'

Makefile

test-cov: istanbul

istanbul:
   istanbul cover _mocha -- -R spec test/spec

coveralls:
   cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js

package.json

"devDependencies": {
   "coveralls": "2.3.0"
}