chore(test): Use dedicated test script to catch errors

The way we were running our unit tests does not catch fatal errors in
the unit test run, even though they return non-zero status codes.

By using a dedicated script to run the tests, with the `pipefail`
option, we can catch them.

Connects pelias/pelias#744

bin/units

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+# run tests with pipefail to avoid false passes
+# see https://github.com/pelias/pelias/issues/744
+set -o pipefail
+
+node test/run.js | npx tap-spec

package.json

@@ -6,7 +6,7 @@
   "homepage": "https://github.com/pelias/pbf2json",
   "license": "MIT",
   "scripts": {
-    "units": "node test/run.js | tap-spec",
+    "units": "./bin/units",
     "test": "npm run units",
     "pretest": "test/pretest.sh",
     "end-to-end": "npm run pretest; node test/end-to-end.js;",