title: Can not run `Karma` tests on Linux server
body: <p>I setup <code>karma</code> tests on my project and runs well on my Mac OSX.
  However it fails on my linux server.</p>
  
  <p>server info:
      $ uname -a
      Linux sz-mc-01 3.13.0-65-generic #106-Ubuntu SMP Fri Oct 2 22:08:27 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux</p>
  
  <p>error output:</p>
  
  <pre><code>26 04 2016 15:06:38.065:INFO [launcher]: Starting browser PhantomJS
  26 04 2016 15:06:38.069:ERROR [launcher]: No binary for PhantomJS browser on your platform.
  Please, set "PHANTOMJS_BIN" env variable.
  </code></pre>
  
  <p>I set "PHANTOMJS_BIN" and rerun, the error is</p>
  
  <pre><code>$ export PHANTOMJS_BIN=node_modules/phantomjs/bin/phantomjs 
  
  26 04 2016 15:20:32.857:INFO [launcher]: Starting browser PhantomJS
  26  04 2016 15:20:32.935:ERROR [phantomjs.launcher]: internal/child_process.js:274
  var err = this._handle.spawn(options);
                       ^
  
  TypeError: Bad argument
  at TypeError (native)
  at ChildProcess.spawn (internal/child_process.js:274:26)
  at exports.spawn (child_process.js:362:9)
  at Object.&lt;anonymous&gt; (/mnt/jenkins/workspace/Website_BridgePlus/node_modules/phantomjs/bin/phantomjs:22:10)
  at Module._compile (module.js:397:26)
  at Object.Module._extensions..js (module.js:404:10)
  at Module.load (module.js:343:32)
  at Function.Module._load (module.js:300:12)
  at Function.Module.runMain (module.js:429:10)
  at startup (node.js:139:18)
  
  26 04 2016 15:20:32.937:ERROR [launcher]: Cannot start PhantomJS
  </code></pre>
  
  <p>Any ideas?</p>