ci - dont attempt to submit coveralls if not configured

package.json

@@ -13,7 +13,7 @@
     "test-unit": "METAMASK_ENV=test mocha --require test/helper.js --recursive \"test/unit/**/*.js\"",
     "single-test": "METAMASK_ENV=test mocha --require test/helper.js",
     "test-integration": "npm run buildMock && npm run buildCiUnits && testem ci -P 2",
-    "test-coverage": "nyc npm run test-unit && nyc report --reporter=text-lcov | coveralls",
+    "test-coverage": "nyc npm run test-unit && if [ $COVERALLS_REPO_TOKEN ]; then nyc report --reporter=text-lcov | coveralls; fi",
     "ci": "npm run lint && npm run test-coverage && npm run test-integration",
     "lint": "gulp lint",
     "buildCiUnits": "node test/integration/index.js",