[INTERNAL] Coveralls: Use parallel setting to reduce number of PR comments

As per https://docs.coveralls.io/parallel-build-webhook

Author: RandomByte

.travis.yml

@@ -6,3 +6,6 @@ node_js:
 
 after_script:
 - npm run report-coveralls
+
+notifications:
+  webhooks: https://coveralls.io/webhook

package.json

@@ -35,7 +35,7 @@
 		"version": "git-chglog --next-tag v$npm_package_version -o CHANGELOG.md && git add CHANGELOG.md",
 		"postversion": "git push --follow-tags",
 		"release-note": "git-chglog -c .chglog/release-config.yml v$npm_package_version",
-		"report-coveralls": "nyc report --reporter=text-lcov | coveralls"
+		"report-coveralls": "nyc report --reporter=text-lcov | COVERALLS_PARALLEL=true coveralls"
 	},
 	"files": [
 		"index.js",