build: run coveralls for unit test coverage

.coveralls.yml

@@ -0,0 +1 @@
+repo_token: DvrDb09a8vhPlVf6DT4cGBjcFOi6DfZN1

.travis.yml

@@ -18,3 +18,5 @@ script:
   - npm run regtest
   - npm run test
   - npm run jshint
+after_success:
+  - npm run coveralls

package.json

@@ -36,7 +36,8 @@
     "test": "mocha -R spec --recursive",
     "regtest": "./scripts/regtest",
     "jshint": "jshint --reporter=node_modules/jshint-stylish ./lib",
-    "coverage": "istanbul cover _mocha -- --recursive"
+    "coverage": "istanbul cover _mocha -- --recursive",
+    "coveralls": "./node_modules/.bin/istanbul cover ./node_modules/mocha/bin/_mocha --report lcovonly -- --recursive -R spec && cat ./coverage/lcov.info | ./node_modules/coveralls/bin/coveralls.js"
   },
   "tags": [
     "bitcoin",
@@ -69,6 +70,8 @@
     "benchmark": "1.0.0",
     "bitcore-p2p": "^1.1.0",
     "chai": "^3.5.0",
+    "coveralls": "^2.11.9",
+    "istanbul": "^0.4.3",
     "jshint": "^2.9.2",
     "jshint-stylish": "^2.1.0",
     "mocha": "^2.4.5",