Fix Travis script

package.json

@@ -11,7 +11,7 @@
     "test": "xo --quiet && npm run ava",
     "ava": "npx ava --concurrency 1 # Unfortunately have to do this so we don't try to bind to the same port multiple times",
     "coverage": "nyc npm test && nyc report --reporter=html",
-    "travis": "nyc npm test && nyc report --reporter=text-lcov | coveralls",
+    "travis": "npx nyc npm test && npx nyc report --reporter=text-lcov | coveralls",
     "document": "documentation build index.js -f html -o docs --config documentation.yml",
     "prepublishOnly": "npm test",
     "preversion": "npm test"