title: Mocha + Chai command line exit with error code number equal test fail count
body: <p>I am really new to Node, and am trying to create a stand alone program. I am using Mocha and Chai to test my functions (new at this as well), and I run them with this node run script:</p>
  
  <pre><code>"test": "mocha tools/testSetup.js \"src/**/*.spec.js\" --reporter progress"
  </code></pre>
  
  <p>(I tried without the reporter option as well). Tests run fine, when a test fails it keeps running the rest, and then creates a (quite verbose) report of what failed. But then the test suit exits node with an error code equals to the number of tests that failed, so if three tests failed then the error code is 3, if no tests failed then the error code is 0. This makes an awful output when at least one test fails, similar to when the application crashes.</p>
  
  <p>Is this by design? am I supposed to do something to "catch" the error? Or am I doing something wrong and the exit code should actually be just 0 regardless of tests failing?</p>