CI should fail when Karma has issues running tests

[abraham]

Even with #157 having tests fail to run the CI passes. If the tests fail to run CI needs to fail.

https://circleci.com/gh/abraham/nutmeg-cli/259

10 01 2018 05:53:00.028:INFO [Firefox 47.0.0 (Linux 0.0.0)]: Connected on socket hzCZIQO9hf5qv7xGAAAB with id 80594156
WARN: 'Custom Elements: `Element#insertAdjacentElement` was not patched.'
Firefox 47.0.0 (Linux 0.0.0) ERROR
  {
    "message": "SyntaxError: missing = in const declaration\nat dist/ci-test.bundled.js:1579:19\n\n",
    "str": "SyntaxError: missing = in const declaration\nat dist/ci-test.bundled.js:1579:19\n\n"
  }

https://travis-ci.org/abraham/nutmeg-cli/jobs/327924488

12 01 2018 00:10:01.108:ERROR [launcher]: Cannot start ChromeHeadless
	[0112/001000.972590:FATAL:setuid_sandbox_host.cc(157)] The SUID sandbox helper binary was found, but is not configured correctly. Rather than run without sandboxing I'm aborting now. You need to make sure that /opt/google/chrome/chrome-sandbox is owned by root and has mode 4755.
Failed to generate minidump.
12 01 2018 00:10:01.108:ERROR [launcher]: ChromeHeadless stdout: 
12 01 2018 00:10:01.108:ERROR [launcher]: ChromeHeadless stderr: [0112/001000.972590:FATAL:setuid_sandbox_host.cc(157)] The SUID sandbox helper binary was found, but is not configured correctly. Rather than run without sandboxing I'm aborting now. You need to make sure that /opt/google/chrome/chrome-sandbox is owned by root and has mode 4755.
Failed to generate minidump.
12 01 2018 00:10:01.109:ERROR [launcher]: ChromeHeadless failed 2 times (cannot start). Giving up.

[abraham]

Fix with #176