title: Trouble running PHPUnit in Travis Build
body: <p>I am having some trouble running PHPUnit from Travis.</p>
  
  <p>My travis configuration is simple</p>
  
  <pre><code>language: php
  php:
    - 7.0
    - 7.1
  script: phpunit
  </code></pre>
  
  <p>And my phpunit.xml is as follows,</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;phpunit bootstrap="vendor/autoload.php"&gt;
      &lt;testsuites&gt;
          &lt;testsuite name="Basic Test Suite"&gt;
              &lt;directory suffix=".php"&gt;./tests/&lt;/directory&gt;
          &lt;/testsuite&gt;
      &lt;/testsuites&gt;
  &lt;/phpunit&gt;
  </code></pre>
  
  <p>And my composer.json</p>
  
  <pre><code>{
      "name": "nikhilkuria/nikeandphp",
      "description": "A PHP library used to work with Nike+ API",
      "type": "library",
      "authors": [
          {
              "name": "nikhilkuria",
              "email": "nikhilkuria@gmail.com"
          }
      ],
      "require": {
          "monolog/monolog": "^1.22"
      },
      "require-dev": {
        "phpunit/phpunit": "5.7.*"
      },
      "autoload": {
          "psr-4": {"NikeAndPhp\\": "src/NikeAndPhp"}
  }
  }
  </code></pre>
  
  <p>The problem is that Travis is not able to find my autoload.php. This is what i see in travis logs,</p>
  
  <p>Cannot open file "/home/travis/build/nikhilkuria/nikeandphp/vendor/autoload.php".</p>
  
  <p>The entire logs are <a href="https://travis-ci.org/nikhilkuria/nikeandphp/jobs/205474909" rel="nofollow noreferrer">here</a>.</p>
  
  <p>What seems to be missing here?</p>